Human Rights Watch said scores of people after a helicopter dropped 'barrel bombs'.
United Nations said Damascus agreed to a ceasefire while experts inspect gs attack sites.
The six negotiators had been trying to set up talks between the Sunni town of al-Zara and the Alawite.
The 11 Western and Arab countries reached an agreement to send military support to aid Syrian rebels.
Western officials will meet the commander of the rebel force to discuss new aid.
Rebels continued to suffer more casualties as the army tightened their grip of Syria.