Syrian forces are bombarding a town in the province of Hama for the 17th straight day, activists say, as the Arab League discusses a peace plan to end a year of fighting in Syria.
Government troops stormed the rebel bastion of Qalaat al-Madiq, said the Syrian Observatory for Human Rights.
The UN and the Arab League have called on Syria to adopt the plan.
But Syria has said it will not address any initiative from the Arab League, from which it was suspended last year.
The plan put forward by UN-Arab League envoy Kofi Annan calls for a commitment from all parties to stop armed violence; a daily two-hour ceasefire to allow aid to get through; and media access to areas affected by fighting.
On Tuesday, the UN said the Syrian government had agreed to accept the plan - a claim met by scepticism from anti-government activists.
But on Wednesday, a Syrian government spokesman told the BBC: "Since our membership was suspended, we deal with other Arab countries on a bilateral level only.
"Therefore, we will not be dealing with or addressing any initiative that comes out of the Arab League at any level," Jihram Maqdessy said.
Syrian forces stormed Qalaat al-Madiq and nearby villages in Hama after a siege lasting more than two weeks, the UK-based Syrian Observatory for Human Rights said on its website.
Their claim cannot be independently verified, as Syria severely restricts journalists' freedom of movement.
One activist said thousands of people had fled the area, including the rebels, who did not have enough weapons to fight back, Reuters reported.
More than 40 people were killed in Qalaat al-Mandiq in recent days, the Observatory said.
Meanwhile, shelling continued around Homs, Syria's third-largest city and the scene of a major offensive by government forces last month, activists said.
UN human rights commissioner Navi Pillay accused the Syrian government of systematically detaining and torturing children.
In an interview with the BBC, Ms Pillay said President Bashar al-Assad bore command responsibility for the abuses carried out by his security forces and would face justice.
"Factually, there is enough evidence pointing to the fact that many of these acts are committed by the security forces [and] must have received the approval or the complicity at the highest level," Ms Pillay said.
"Because President Assad could simply issue an order to stop the killings and the killings would stop."
Ms Pillay said she believed that the UN Security Council had enough reliable information to warrant referring Syria to the International Criminal Court (ICC).
Late on Tuesday, several Syrian dissident groups meeting in Istanbul agreed to recognise the Syrian National Council (SNC) as the official representative of the Syrian people.
But the BBC's Jonathan Head, in Istanbul, says their disunity was openly on display, with constant disputes and walkouts.
The UN says more than 9,000 people have been killed since the uprising against President Assad began a year ago.