Attempts to diffuse the growing crisis in Ukraine have floundered as Russia accused the government of sending 15,000 troops to the border and separatists from the troubled east defied President Vladimir Putin's request to postpone a referendum on independence.
"The referendum will be on May 11," Miroslav Rudenko, co-chairman of the self-declared government of the "Donetsk People's Republic" (DPR), was quoted as saying.
The decision to hold the vote as planned was unanimous, said Denis Pushilin, co-chairman of the DPR added.
Despite Putin urging separatists to delay a vote, Ukraine said its anti-terror operation would continue. At least 34 people, including many rebels, have died in that offensive which was launched last week, the government said.
Meanwhile, Russia's Defence Ministry claimed Ukraine had assembled 15,000 troops on its border with Russia and demanded the West to stop "cynically misinforming" the international community about events on the frontier between the two countries.
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
2/39 Ukraine crisis
Children were transferred from orphanages in Donetsk and Makeyevka to escape the fighting between the Ukrainian army and pro-Russian separatists
3/39 Ukraine crisis
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
4/39 Ukraine crisis
A view inside the Youth Culture Centre destroyed by pro-Russian separatists in Donetsk
5/39 Ukraine crisis
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
6/39 Ukraine crisis
A boy ascends the stairs of a bomb shelter after the shelling in the Petrovskiy district in Donetsk
7/39 Ukraine crisis
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
8/39 Ukraine crisis
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
9/39 Ukraine crisis
Medical workers carry a wounded pro-Russian militant on a stretcher after armed clashes occured between pro-Russian gunmen and Ukrainian troops in Slavyansk
10/39 Ukraine crisis
A member of a newly-formed pro-Russian armed group called the Russian Orthodox Army mans a barricade near Donetsk airport
11/39 Ukraine crisis
Black smoke rises from a shot down Ukrainian Army helicopter outside Slovyansk
12/39 Ukraine crisis
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
13/39 Ukraine crisis
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
14/39 Ukraine crisis
A bloodstained icon of Jesus is seen among blood soaked shattered glass atop a wrecked truck near the Donetsk airport
15/39 Ukraine crisis
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
16/39 Ukraine crisis
A woman reacts after seeing the lifeless body of a man killed by shrapnel following a shelling from Ukrainian government forces in Slovyansk
17/39 Ukraine crisis
Pro-Russian militants take position on the roof of the international airport of the eastern Ukrainian city of Donetsk
18/39 Ukraine crisis
A woman embraces a pro-Russian separatist from the "East" battalion during a rally in the eastern city of Donetsk
19/39 Ukraine crisis
A Ukrainian helicopter Mi-24 gunship fires its cannons against rebels at the main terminal building of Donetsk international airport
20/39 Ukraine crisis
A pro-Russian gunman changes his position near the airport, outside Donetsk
21/39 Ukraine crisis
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
22/39 Ukraine crisis
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!"
23/39 Ukraine crisis
An elderly woman leans against the chest of a pro-Russian gunman in Lenin square in Donetsk
24/39 Ukraine crisis
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
25/39 Ukraine crisis
Ukrainian troops stand guard at a checkpoint on the road near the eastern city of Izum, Donetsk
26/39 Ukraine crisis
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
27/39 Ukraine crisis
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
28/39 Ukraine crisis
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
29/39 Ukraine crisis
Members of a local election commission sort ballots as they start counting votes of referendum on the status of Luhansk region in Luhansk
30/39 Ukraine crisis
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
31/39 Ukraine crisis
Members of a local election commission empty ballot boxes as they start counting votes after a referendum, at a polling station in Lugansk
32/39 Ukraine crisis
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
33/39 Ukraine crisis
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
34/39 Ukraine crisis
Voters visit a polling station to take part in the referendum on the status of Donetsk
35/39 Ukraine crisis
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
36/39 Ukraine crisis
A statue of Lenin is placed in front of a pro-Russian barricade on the outskirts of the eastern Ukrainian town of Slavyansk
37/39 Ukraine crisis
A feamle veteran (C) sings during 'Victory Day' celebrations in Donetsk
38/39 Ukraine crisis
People stand near the burning Mariupol police station
39/39 Ukraine crisis
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
Earlier, Mr Putin had appeared to be softening his tone in the confrontation with the West by asking for pro-Russian activists to postpone a referendum on autonomy in Ukraine's troubled east ahead of a presidential vote on 25 May.
The presidential elections were "a step in the right direction", Mr Putin added, a remark that came heavily in contrast to comments made by his spokesperson describing them as "absurd" the day before.
The European Union has warned the referendum in eastern Ukraine "would have no democratic legitimacy and could only further worsen the situation."
The ballot is due to take place on Sunday and asks: “Do you support the act of proclamation of independent sovereignty for the Donetsk People's Republic?”
Separatist leaders in Donetsk and Luhansk say they will consider Mr Putin's request to postpone the vote and say they will put the matter "before people's councils".
The White House has responded by dismissing the vote as “illegal” and called for it to be cancelled instead of delayed.
In an unexpected move, Mr Putin said Russian troops have been pulled back to their training grounds and locations for “regular exercises”, but he did not specify whether those locations were in areas near its border with Ukraine.
But Nato and the US said they saw no indication of a Russian pullback, and the pro-Russia insurgents behind the referendum have not agreed to go along with Mr Putin's proposal.
Many had feared that Sunday's vote would be a flashpoint for further violence between the rebels and Ukrainian troops.
Mr Putin said: “We believe that the most important thing is to create direct, full-fledged dialogue between the Kiev authorities and representatives of south-east Ukraine.
”Because of this, we ask that representatives of south-east Ukraine, supporters of federalisation in the country, postpone the May 11 referendum in order to create the necessary conditions for such a dialogue”
But it is unclear how much influence Moscow has with the insurgents, and many Donetsk residents appear eager to go ahead with the vote.
Additional reporting by agencies