Geneva: Syria`s main opposition group says 1,000 people have been killed by government forces in the last eight days.
A spokeswoman for the Syrian National Council says troops loyal to President Bashar Assad have intensified their onslaught in opposition areas despite saying it would accept a UN peace plan.
SNC spokeswoman Bassma Kodmani says 160 people were killed in Syria on Monday alone.
Kodmani told reporters in Geneva on Tuesday that regime forces have used heavy weapons including anti-aircraft guns against civilians in apparent defiance of an agreement to begin a cease-fire April 10.
She says the humanitarian situation on the ground is "dramatically deteriorating".
Earlier in the day Syrian activists had reported of military attacks and arrest raids in towns across Syria and denied claims by the foreign minister that regime forces have begun pulling out of some areas in compliance with a UN-brokered truce.
French Foreign Ministry spokesman Bernard Valero dismissed Syria`s claims of a withdrawal as "a new expression of this flagrant and unacceptable lie" and British Foreign Secretary William Hague accused Damascus of using the cease-fire deadline "as a cover for intensified military efforts to crush Syria`s opposition."
Even close ally Russia seemed critical of President Bashar Assad`s regime.
"We believe that their efforts to implement the plan could have been more active and resolute," said Russian Foreign Minister Sergey Lavrov.
Activists said they have seen no signs of the large-scale troop pullback that Assad committed to under the cease-fire brokered by UN-Arab League envoy Kofi Annan. Military forces were supposed to withdraw from towns and villages on Tuesday with both sides ceasing all hostilities by 6 am 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 been deeply skeptical that the regime would comply with the cease-fire because Assad has violated previous agreements and his forces escalated attacks on opposition strongholds in the weeks leading up to the deadline. At the same time, options for ending the fighting appear to be dwindling with the international community unwilling to intervene militarily.
Annan has not commented on the apparent breakdown of his plan, and his spokesman, Ahmad Fawzi, would only say Tuesday that it`s up to the UN Security Council to decide what to do next.
As claims and counterclaims about Syrian truce violations flew across the region Tuesday, Annan toured a camp in Turkey, near the Syrian border where hundreds of Syrian refugees greeted him with chants of "Syria, Syria, Syria!"
The Britain-based Syrian Observatory for Human Rights, an activist group, said there were no indications the Syrian regime was pulling back forces. Instead, the group and activists in Syria reported shelling attacks and raids in several locations in the north, center 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."
In northern Idlib and central Hama province, troops backed by helicopters were firing heavy machine guns to try to flush out opposition fighters, al-Yassin said. Regime forces detained residents and set four homes on fire in Idlib`s Ariha village and a contingent of 50 army vehicles entered the town of Kfar Zeita in Hama province, he said.
The Observatory said troops also fired shells at the town of Mareh in northwestern Syria and at two neighborhoods in the central city of Homs. Additional raids were reported in two southern village, the group said. Mohammed Saeed, a resident of the Damascus suburb of Douma, said tanks were patrolling the streets, as they have in recent days. Some tanks bore graffiti reading "Assad`s shield," he said.
In Moscow, Syrian Foreign Minister Walid Moallem claimed the regime is complying with the truce deal.
"We have already withdrawn forces and army units from several Syrian provinces," he said in a joint news conference with Lavrov, the Russian foreign minister.
There were signs that the regime was stalling for time when it made new, last-minute demands over the weekend, saying it could not withdraw troops from towns without written guarantees that the rebels would lay down their arms.
"It should be everyone`s working assumption that the Syrian regime will seek to draw out every step at every opportunity; it will assent and then object, repeatedly," said Yezid Sayigh, an analyst at the Carnegie Middle East Center in Beirut.
Moallem appeared to raise another new demand, saying that the cease-fire must start simultaneously with the deployment of the international observer mission. The deployment of observers was one of the terms of Annan`s plan.
And in another apparent shift, Moallem said Syria wants the truce guarantees to be issued by Annan, not by the opposition fighters.
"We did not ask for guarantees from armed terrorist groups that practice killing, take hostages and destroy infrastructure. We want guarantees from Annan," he said in Moscow.
The Syrian opposition has said that while it is ready to go along with the Annan plan, it does not recognize the Assad regime and would not provide written guarantees.
Unlike previous peace plans, this one has the backing of Assad allies Russia and China because it did not call for the Syrian leader to step aside ahead of talks on a political transition.
But even Russia seemed to be critical of Damascus.
Lavrov said the Syrian government could have done more to comply with the plan, adding that "we spoke about it quite frankly" to Syrian officials.
Yet he also seemed to be trying to shift equal blame on the opposition for the difficulties in implementing the truce, repeating Russia`s call for the West to pressure rebel fighters to halt violence.
"The United States and other countries that have stable contacts with various Syrian opposition groups should not blame everything on Russia and China, but use their own influence to force everyone to stop firing in each other," he said.
Russia and China have shielded Syria from UN Security Council condemnation in the past, arguing that only negotiations with the regime offer a way out of the crisis.
Lavrov also called for a speedy deployment of international observers — including Russians — in the country. Such a deployment is key to making a truce stick and a small contingent could be dispatched quickly, he said.
Sending UN observers currently posted on the Golan Heights, a strategic plateau captured by Israel from Syria in 1967, was being discussed, he said.
"The UN Secretariat has asked Russia and other countries to give their consent to include their citizens with the mission on the Golan Heights. We have agreed and we expect others to do the same quickly," Lavrov said.
The 13-month uprising against Assad`s regime has turned increasingly militarized in response to a brutal regime crackdown. The fighting is also spilling across Syria`s borders, raising the risk of a regional conflagration. The UN says has claimed more than 9,000 lives.
On Monday, Syrian forces opened fire across the Turkish and Lebanese borders, killing a TV journalist in Lebanon and two people in a refugee camp in Turkey. Several people were also wounded in the shooting.
Turkish Prime Minister Recep Tayyip Erdogan on Tuesday accused Syria of violating the border and said his country is considering what steps to take in response, including measures "we don`t want to think about." He did not elaborate.
Turkey, which has already given shelter to some 24,000 Syrian refugees, has floated the idea of creating security zones along its border, a step that could drag the Turkish military into the conflict.
Moallem on Tuesday accused Turkey of helping fuel the violence. Turkey "is hosting gunmen, giving them training camps, allowing them to cross the border and smuggle weapons," he said. "All these acts contradict Kofi Annan`s mission."
Asked about the possibility of a Turkish buffer zone on the border, he said that "Syria is a sovereign state and has the right to defend its sovereignty against any violation of this sovereignty."