Vladimir Putin has called for the Ukrainian army to immediately end its operation against pro-Russian rebels after dozens were killed in bloody clashes.
In his first public comments on Ukraine since Sunday's presidential election, the Russian President also stepped up pressure on Kiev to start a dialogue with rebel leaders as fighting continued.
The Kremlin said Mr Putin had spoken to the Italian Prime Minister, Matteo Renzi, by telephone and “underscored the need for an immediate halt to the punitive military operation in the southeastern regions and the establishment of peaceful dialogue between Kiev and representatives of the regions".
Russia said it started to withdraw troops stationed along its border with Ukraine since the start of the crisis but Nato said many remain.
Sergei Lavrov, Russia's Foreign Minister, reiterated calls for an immediate end to violence, according to Russian news agencies.
He said halting bloodshed in Ukraine's southeast was the most important task for the authorities in Kiev and the new President and warned that efforts to put down the separatists could backfire.
At least 30 rebels were killed in heavy fighting with the Ukrainian army in Donetsk on Monday and the Ukrainian military has taken back control of the besieged airport.
Oleksandr Lukyanchenko, the Mayor of Donetsk, claimed 48 people, including two civilians, were killed on the day, while rebel leaders said the death toll could reach 100.
In pictures: The Ukraine crisis
In pictures: The Ukraine crisis
1/39 Ukraine crisis
Ukrainian soldiers from the 'Azov' battalion guard their base in Mariupol, Donetsk
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Children were transferred from orphanages in Donetsk and Makeyevka to escape the fighting between the Ukrainian army and pro-Russian separatists
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Ukrainian servicemen captured by pro-Russian separatists sit on the ground as they are assigned to clean a street in Snizhne in the Donetsk region
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A view inside the Youth Culture Centre destroyed by pro-Russian separatists in Donetsk
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A woman holds a portrait of her dead son as she speaks during a rally in front of Ukrainian President Petro Poroshenko's office in Kiev
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A boy ascends the stairs of a bomb shelter after the shelling in the Petrovskiy district in Donetsk
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A medic looks at thirty coffins prepared for the funerals of pro-Russian rebels killed during heavy fighting at Donetsk airport, outside a Donetsk morgue
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Relatives mourn near the coffin of Mark Zverev, a taxi driver shot dead during clashes at the Donetsk airport between Ukrainian troops and the pro-Russian rebels, during his funeral in the village of Grabari on the outskirts of Donetsk
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Medical workers carry a wounded pro-Russian militant on a stretcher after armed clashes occured between pro-Russian gunmen and Ukrainian troops in Slavyansk
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A member of a newly-formed pro-Russian armed group called the Russian Orthodox Army mans a barricade near Donetsk airport
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Black smoke rises from a shot down Ukrainian Army helicopter outside Slovyansk
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A woman is overcome with emotion as she looks at blood stains and damage around a wrecked truck of supporters of the self-proclaimed 'Donetsk People's Republic' on road leading to the Donetsk International Airport
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A local man looks at damage near a wrecked truck of supporters of the self-proclaimed 'Donetsk People's Republic' on road leading to the Donetsk International Airport
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A bloodstained icon of Jesus is seen among blood soaked shattered glass atop a wrecked truck near the Donetsk airport
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A family member attends a funeral for Olga Prokhorenko (60) who was killed by shrapnel after Ukrainian government forces shelled their location, during the funeral in Slovyansk
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A woman reacts after seeing the lifeless body of a man killed by shrapnel following a shelling from Ukrainian government forces in Slovyansk
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Pro-Russian militants take position on the roof of the international airport of the eastern Ukrainian city of Donetsk
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A woman embraces a pro-Russian separatist from the "East" battalion during a rally in the eastern city of Donetsk
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A Ukrainian helicopter Mi-24 gunship fires its cannons against rebels at the main terminal building of Donetsk international airport
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A pro-Russian gunman changes his position near the airport, outside Donetsk
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A pro-Russian gunman aims his weapon near the airport, outside Donetsk. Ukraine's military launched air strikes against separatists who had taken over the airport in the eastern capital of Donetsk in what appeared to be the most visible operation of the Ukrainian troops since they started a crackdown on insurgents
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Pro-Russians ride on a truck in Donetsk. A convoy of an armored personnel carrier and seven trucks carrying several hundred heavily armed men drove through central Donetsk and gunmen got out of the trucks, stood to attention and gave shots in the air in jubilation as a crowd of several thousand supporters cheered them and chanted: "Heroes!"
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An elderly woman leans against the chest of a pro-Russian gunman in Lenin square in Donetsk
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Pro-Russian militants guard a psychiatric hospital after shell explosions during the fighting between pro-Russian militants and the Ukrainian army, in Semyonovka village, outside Slavyansk
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Ukrainian troops stand guard at a checkpoint on the road near the eastern city of Izum, Donetsk
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Members of the Democratic Alliance party take part in a performance in front of the French embassy in Kiev. Protesters set up a pool with the blood of animals and models of warships in a protest against French plans for the sale of two Mistral helicopter carriers to the Russian Navy
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A man carries a portrait of pro-Russian activist Vadim Hudich, who was killed in a shooting incident at the head of a funeral procession in the eastern Ukranian town of Krasnoarmeisk
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A voter is seen inside a voting booth at a polling station during the referendum on the status of Donetsk region in the eastern Ukrainian city of Donetsk
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Members of a local election commission sort ballots as they start counting votes of referendum on the status of Luhansk region in Luhansk
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Members of a local election commission empty a ballot box as they start counting votes of the referendum on the status of Donetsk region in Donetsk
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Members of a local election commission empty ballot boxes as they start counting votes after a referendum, at a polling station in Lugansk
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Local residents watch as others give first aid to a man who was shot in the leg by Ukranian militia in the village of Krasnoarmisk. Eyewitness said that Ukranian militia tried to stop the referendum voters briefly taking the City Hall of Krasnoarmisk, where unarmed pro-Russian supporters were gathering. Reportedly the Ukranian militia came out out the building and started shooting at the people, killing at least one man and leaving at least two others injured
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Members of a local election commission count votes after a referendum organized by the so-called Donetsk People's Republic members at a polling station in Donetsk
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Voters visit a polling station to take part in the referendum on the status of Donetsk
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An Armoured Personnel Carrier (APC) with a Russian flag drives through the center of Slaviansk during the day of referendum organized by the so-called Donetsk People's Republic members in Slavyansk
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A statue of Lenin is placed in front of a pro-Russian barricade on the outskirts of the eastern Ukrainian town of Slavyansk
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A feamle veteran (C) sings during 'Victory Day' celebrations in Donetsk
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People stand near the burning Mariupol police station
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Ukrainian soldiers stand guard beside an armoured personnel carrier at a checkpoint in Mariupol. Ukrainian forces seized the rebel-held city hall in the eastern port city of Mariupol, driving out pro-Russian activists, then withdrew, making no attempt to hold onto the building
Government forces used fighter jets and helicopter gunships against the pro-Russian rebels who had taken over the city’s international airport on Monday.
The newly-elected President, Petro Poroshenko, had vowed to crush the rebellion in the east of the country “in a matter of hours”.
One insurgent, who did not give his name, said outside the hospital in Donetsk that 30 bodies of his fellow insurgents were taken there.
The lorry carrying the bodies was still parked outside the hospital, waiting for explosives experts to check for any unexploded weapons, he said.
Sustained artillery and gunfire was heard from the airport in Donetsk on Monday and dense black smoke could be seen in the air.
Many flights were delayed or cancelled and access to the airport was blocked by police.
The air strikes against the separatists in control of Donetsk airport appeared to be the most visible Government military operation yet since it started a crackdown on insurgents last month.
Two civilians, including an elderly woman, were reportedly killed by stray bullets during the fighting at nearby Donetsk railway station.
The chaos continued on Tuesday and posters went up in the streets telling people how to act if shooting broke out and where bomb shelters were located. Schools were closed and parents were warned to keep their children indoors.
On the road to Donetsk airport, Reuters journalists saw blood-spattered and bullet-riddled trucks of the kind the separatist fighters have been using.
A Kamaz truck lay wrecked on the airport road, covered in blood and completely riddled with bullet holes. Blood had spattered across the entire roadway and even reached a billboard seven metres above, they said.
Pro-Russian separatists reportedly first stormed the airport early on Sunday, ejecting the airport security staff and Ukrainian soldiers guarding the site.
It was the second time this month that they have occupied the international airport, whose vast new terminal was built for the 2012 European Football Championships.
Known as the “chocolate king”, confectionery billionaire Mr Poroshenko won Sunday's presidential vote.
He has vowed to negotiate a peaceful end to the crisis but dubbed pro-Russian rebels “terrorists” and compared them to Somali pirates.
Russia has supported the decentralisation of Ukraine’s government to give the regions more autonomy and wants troops to be withdrawn from eastern and southern parts of the country that have seen unrest.
Additional reporting by Associated Press and Reuters