Syrian President Bashar al-Assad's forces rained rockets and bombs down on opposition-held neighbourhoods of the city of Homs, reducing buildings to rubble and killing more than 80 people.
The barrages marked an intensification of a nearly three-week offensive to crush resistance in Homs, one of the focal points of a nationwide uprising against Assad's 11-year rule and its ferocity has caused international outrage.
More than 60 bodies, both rebel fighters and civilians, were recovered from one area of Homs' Babo Amro neighbourhood after an afternoon bombardment, adding to 21 killed earlier in the day, activists.
"Helicopters flew reconnaissance overhead then the bombardment started," Homs activist Abu Abei told Reuters.
Videos uploaded by opposition activists showed smashed buildings, deserted streets, and doctors treating wounded civilians in primitive conditions in Baba Amro district, the main target of Assad's wrath.
"President Assad wants to finish the Homs situation by Sunday to prepare for the constitutional referendum. Then he will turn to Idlib," a Lebanese official who is close to the Syrian government told Reuters in Beirut.
The devastation has caused an outcry but the carnage only showed how helpless Western powers are in their efforts to stop the bloodshed.
The United States, which so far has been against military intervention in Syria, hinted however that if a political solution to the crisis was impossible it might have to consider other options.
Residents fear Assad will subject the city to the same treatment as his late father Hafez inflicted on the rebellious town of Hama 30 years ago, when 10,000 were killed.
The worsening humanitarian situation in Homs and other embattled towns is bound to dominate "Friends of Syria" talks in Tunis on Friday involving the United Staes, European and Arab countries, Syria's neighbour Turkey and other nations clamouring for Assad to halt the bloodshed and relinquish power.
In a chilling example of the repression, activists also said troops and militia loyal to Assad summarily executed 27 young men on Tuesday in northern villages.
Several YouTube videos taken by local activists in the northern Idlib area, which could not be independently confirmed, showed the bodies with bullet wounds to the head or chest and hands tied lying dead in streets.
In an effort to bring relief to starving and bloodied civilians in Homs, the International Committee of the Red Cross was in talks with the Syrian government on Wednesday to arrange a pause in the fighting.
Russia, Assad's main arms supplier and seen as retaining some leverage over him, said it was seeking safe passage of aid convoys to civilians trapped in the violence.
France also appealed to Assad to halt the onslaught to allow safe passage for aid.
French President Nicolas Sarkozy called the deaths of the two journalists, French photographer Remi Ochlik and American Marie Colvin of Britain's Sunday Times, an assassination and said the Assad era had to end.
"That's enough now," Sarkozy said. "This regime must go and there is no reason that Syrians don't have the right to live their lives and choose their destiny freely. If journalists were not there, the massacres would be a lot worse."
The Syrian Network for Human Rights said government forces killed a total of 21 civilians in Homs on Wednesday, mostly in bombardments on Baba Amro, a Sunni Muslim district opposed to Syria's Alawite ruling class.
Several hundred people have been killed in the daily bombardments by the besieging forces using artillery, rockets, sniper fire and Soviet-built T-72 tanks.
Ground forces have held off from entering opposition areas as rebel fighters allied to the opposition are ready to take them on.
The army is preventing medical supplies from going in and electricity is cut off 15 hours a day, activists say. Hospitals, schools and most workplace and shops are shut and government offices have also closed.
As the Lebanese official explained it, Assad wants to batter Homs into submission before a referendum this Sunday on a new constitution leading to multi-party elections as a way to resolve the crisis.
His plan has the support of his allies Russia and China but Western powers have dismissed it as a joke under the present circumstances and the Syrian opposition have called for a boycott.
The ICRC issued a public appeal on Tuesday to Syrian authorities and rebels to agree on a two-hour truce each day to allow life-saving supplies to reach civilians and to evacuate the growing number of wounded from Homs and elsewhere.
ICRC spokeswoman Carla Hadda said she was unable to say if and when a deal might be clinched.
"The situation is difficult and we are worried it is deteriorating," she told Reuters on Wednesday. "Everybody is focused on Homs but we shouldn't turn a blind eye to what is happening in other areas."
Army bombardments on the town of Khan Sheikhoun, north of Homs on the Damascus-Aleppo highway in Idlib province, killed two people on Wednesday, the London-based Syrian Network said.
Russian foreign ministry spokesman Alexander Lukashevich said Moscow has asked the U.N. secretary-general to send a representative to liaise with all sides for the safe transit of aid convoys.
The opposition Syrian National Council (SNC) said it was coming to the view that military intervention was the only solution to the crisis.
"There are two evils, military intervention or protracted civil war," senior SNC official Basma Kodmani told a news conference in Paris.
In Washington, officials stressed the Obama administration was still seeking a negotiated solution but also hinted it could reconsider its stance on not arming Syria's opposition.
"We don't want to take actions that would contribute to the further militarisation of Syria, because that could take the country down a dangerous path. But we don't rule out additional measures," White House spokesman Jay Carney said on Tuesday.