About 1,000 people have been killed by Syrian government forces in the last eight days, according to the country’s main opposition group.
A spokeswoman for the Syrian National Council said troops loyal to president Bashar Assad have intensified their onslaught in opposition areas despite saying the regime saying it would accept a UN peace plan.
SNC spokeswoman Bassma Kodmani says 160 people were killed in Syria yesterday alone.
Ms Kodmani told reporters in Geneva that regime forces have used heavy weapons including anti-aircraft guns against civilians in apparent defiance of an agreement to begin a ceasefire today.
She said the humanitarian situation on the ground was “dramatically deteriorating”.
France and Britain accused Syria of deception and even Damascus ally Russia seemed critical of Bashar Assad's regime, with Russian foreign minister Sergey Lavrov complaining that Syria's ``efforts to implement the plan could have been more active and resolute''.
Syrian opposition leaders said they remain committed to the ceasefire brokered by UN-Arab League envoy Kofi Annan, which requires Syrian forces to withdraw from towns and villages today and both sides to cease all hostilities by 6am local time on Thursday.
The truce is widely seen as the last chance for diplomacy, and its collapse could push Syria even closer to an all-out civil war.
The opposition as well as the US and its allies have cast doubt on claims that the regime would comply with the ceasefire because it has violated previous agreements and escalated attacks on opposition strongholds in recent weeks.
At the same time, options for ending the fighting appear to be dwindling with the international community unwilling to intervene militarily.
French foreign ministry spokesman Bernard Valero dismissed Syria’s claims of a withdrawal as “a new expression of this flagrant and unacceptable lie”, while British Foreign Secretary William Hague accused Damascus of using the ceasefire deadline “as a cover for intensified military efforts to crush Syria’s opposition”.
Activists said they have seen no signs of withdrawal by Syrian government troops today.
Instead, regime forces have used heavy weapons including anti-aircraft guns against civilians, Bassma Kodmani, a spokeswoman for the largest opposition group, the Syrian National Council, told reporters in Geneva.
Ms Kodmani estimated that some 1,000 people were killed since Mr Annan announced the ceasefire timeline on April 2.
“So every day is a very, very painful time that is given to the Assad regime,” she said, adding the death toll was based on figures provided by various groups, including the Syrian Arab Human Rights Network.
Syria restricts the access of foreign journalists, and claims about casualties cannot be verified independently. The UN has said previously it believes more than 9,000 people have been killed in the 13-month uprising against Mr Assad.
Mr Annan has not commented on the apparent breakdown of his plan, and his spokesman, Ahmad Fawzi, would only say that it is up to the UN Security Council to decide what to do next.
As claims and counterclaims about Syrian truce violations flew across the region, Mr Annan toured a camp in Turkey, near the Syrian border where hundreds of Syrian refugees greeted him.
The UK-based Syrian Observatory for Human Rights, an activist group, said the Syrian regime gave no indication it was pulling back forces. Instead, the group and activists in Syria reported shelling attacks and raids in several locations in the north, centre and south of the country, it said.
“Soldiers are not being withdrawn from towns and villages,” said Fadi al-Yassin, an activist in the Idlib province close to Turkey. “On the contrary, reinforcements are being sent.”