Syrian warplanes pounded the embattled town of Qusair on Monday as a regime offensive backed by fighters from Lebanon's Hezbollah to retake the town from rebels entered its third week.
The Syrian Observatory for Human Rights reported a fierce overnight onslaught both on the strategic town near the border with Lebanon and slightly farther north in Dabaa.
Dabaa, the site of a disused military airbase that had been seized by rebels battling President Bashar al-Assad's regime, is still partly under insurgent control.
The Britain-based Observatory, which relies on a wide network of activists, medics and others on the ground for its information, said there were numerous dead on both sides, but gave no breakdown.
An estimated 94,000 people have been killed in Syria since a peaceful protest movement that began in March 2011 quickly became an armed revolt when the regime cracked down hard on dissent.
Warplanes bombarded Qusair for the second consecutive day, the Observatory said on Monday.
The activists also reported air strikes on the Al-Hajar al-Aswad district of southern Damascus itself, where pillars of thick dark smoke barrelled into the sky.
It said clashes between soldiers and rebels were ongoing in the Abasiyeen area outside the capital's Jubar neighbourhood.
Again, the rights group was unable to give a casualty figure.
Monday's fighting in Syria came a day after a car bombing in Damascus killed at least nine members of the security forces and the regime said it would allow the Red Cross into Qusair only when the fighting there stopped.
At the United Nations, diplomats said Russia blocked a draft Security Council declaration expressing "grave concern" about the situation in Qusair.
They said Moscow was demanding "wider political discussion" on the issue.
Russia is a key ally of the Syrian regime, which is also backed by Shiite Iran.
On Saturday, UN chief Ban Ki-moon and international aid groups expressed concern about civilians trapped in Qusair, and for between 1,000-1,500 injured residents still in the town of 25,000 people.
But on Sunday, Syrian Foreign Minister Walid Muallem expressed "surprise" at worries about the situation in Qusair "given that no one expressed this concern when terrorists took control of the city and the surrounding area".
France, meanwhile, said that the proposed "Geneva 2" peace conference on ending the bloodshed in Syria could be delayed until next month.
The international community has pinned its hopes for resolving the conflict peacefully on the US-Russian initiative that had been mooted for June in Geneva.
"'Geneva 2' is in my opinion a last-chance conference. I hope it will take place, I think it could take place in July," French Foreign Minister Laurent Fabius said.
Arab states of the six-nation Gulf Cooperation Council said on Sunday they could take measures against Hezbollah which is now openly involved in the Syria conflict, especially in Qusair.
The GCC had "decided to look into taking measures against Hezbollah's interests in the member states," its chief Abdullatif al-Zayani told reporters in the Saudi city of Jeddah.
Bahraini Minister of State for Foreign Affairs Ghanim al-Buainain said that "nobody could cover up Hezbollah's actions in regional countries.
"It is a terrorist organisation and this is how Gulf states see it."