Forces loyal to President Bashar al-Assad also moved on rebel-held enclaves of Damascus a day after shelling killed 21 civilians at the Yarmuk Palestinian refugee camp in the capital, according to a rights watchdog.
Activists were still counting the toll from Thursday, one of the bloodiest days in Syria's uprising, when Kofi Annan quit as international envoy for Syria complaining that his peace plan never received the backing it deserved.
The Syrian Observatory for Human Rights said more than 179 people were killed in Thursday's violence 110 civilians including 14 children, 43 soldiers and 26 rebels.
"Dozens" more civilians and rebels were killed in Al-Arbaeen, a district of the central city of Hama which is under siege by troops, it said, adding that it was hard to establish what had happened as communications were cut.
"The number of martyrs and wounded is not known as bodies were left lying in the streets, regime forces preventing residents from helping the wounded and burying the dead," said the opposition Syrian National Council.
The bloodshed mounted ahead of a vote at the United Nations General Assembly on a Saudi-drafted resolution that condemns Russia and China for blocking tougher action against the Syrian regime at the UN Security Council.
Arab nations have dropped an explicit demand for Assad to quit, however, toning it down in an attempt to secure as large a majority as possible in the 193-member assembly.
Explaining his decision to resign as UN and Arab League envoy for Syria, Annan voiced regret at the "increasing militarisation" of the nearly 17-month conflict.
The former UN secretary general hit out at "continuous finger-pointing and name-calling" at the UN Security Council, which he said had prevented coordinated action to stop the violence.
"I did not receive all the support that the cause deserved," Annan told a hastily arranged news conference in Geneva.
"You have to understand: as an envoy, I can't want peace more than the protagonists, more than the Security Council or the international community for that matter.