Fighting between rebels and troops raged around Damascus Thursday leaving dozens dead as Syria's opposition leader threatened to withdraw an offer of peace talks aimed at ending Syria's two-year conflict.
Leaders of Muslim states at a summit in the Egyptian capital, meanwhile, worked on a draft resolution calling for "serious dialogue" between the opposition and government officials.
Activists and residents reported clashes and heavy shelling in rebel belts around the capital for a second straight day on Thursday as the army pressed a major offensive that a watchdog said had killed at least 64 people in 24 hours.
Among the victims were five civilians, three of them women, who died when mortars slammed into the Palestinian refugee camp of Yarmuk in the south of Damascus, the Syrian Observatory for Human Rights said.
The Observatory and a Syrian security official had on Wednesday reported the launch by President Bashar al-Assad's forces of a fierce offensive on rebel belts on the capital's outskirts, while residents reported the heaviest bombardments in months.
The Britain-based Observatory reported on Thursday that 21 civilians, 32 rebels and 11 soldiers have been killed since the launch of the offensive, which is focused in the southern and eastern outskirts.
It said that rebels on Wednesday attacked a security checkpoint between the northeast Qaboon district and Abassid Square near the centre of the capital, sparking fierce fighting.
Pro-regime daily Al-Watan reported that "terrorists ... who attacked army checkpoints perished at the gates of Damascus on the perimeter of Abassid Square. They could not advance."
"The army is determined to crush terrorism around the capital and big cities, and over the past several days it has launched a qualitative operation and killed dozens of terrorists who dreamt of attacking and entering Damascus," it said.
The Observatory also reported the arrival Thursday of military reinforcements at Daraya, an embattled southwestern suburb of Damascus that has been under continuous army bombardment for months.
Also on the outskirts of the capital, loyalist troops pounded rebel positions across the east and in the south, the Observatory said, as clashes broke out around a military vehicle depot to the northeast.
These areas around Damascus are among the strongest bastions of the rebellion against the Assad regime, which is battling to suppress a revolt since March 2011 that the United Nations says has left more than 60,000 dead.
The Observatory, which gathers its reports from a large network of activists and medics in civilian and military hospitals on the ground, said that 160 people were killed nationwide on Wednesday: 75 rebels, 46 soldiers and 39 civilians.
The intensification of the fighting further dimmed prospects for peace talks as suggested by opposition leader Ahmed Moaz al-Khatib.
The surprise gesture by Khatib, head of the opposition National Coalition, was welcomed by the United States and the Arab League, and was expected to receive the backing of the Organisation of Islamic Cooperation (OIC) meeting in Cairo.
But Damascus has so far ignored it and a key opposing faction has flatly rejected the initiative.
Khatib stepped up the pressure to engage in talks by setting the regime a deadline of Sunday for the release of all women held in Syrian prisons.
"The demand that the women are released means that if there is one single woman still in prison in Syria on Sunday, I consider that the regime has rejected my initiative," Khatib told BBC Arabic.
The Syrian National Council, the main component of the Coalition, has rejected the possibility of any talks, saying it is committed to ousting Assad's regime and protecting the revolution.
A draft OIC resolution calls for "serious dialogue" between the Syrian opposition and government officials "not directly involved in oppression".
Among the leaders taking part in Cairo, Iranian President Mahmoud Ahmadinejad said he wanted his allies in the Syrian regime to negotiate with the opposition for the staging of a free election, in an interview with Egyptian state television.