U.N. observers could smell the stench of burned corpses Friday and saw body parts scattered around a Syrian farming hamlet that was the site of a massacre this week in which nearly 80 men, women and children were reported slain. The scene held evidence of a "horrific crime," a U.N. spokeswoman said.

The observers were finally able to get inside the deserted village of Mazraat al-Qubair after being blocked by government troops and residents, and coming under small arms fire Thursday, a day after the slayings were first reported.

In central Damascus, rebels brazenly battled government security forces in the heart of the capital Friday for the first time, witnesses said, and explosions echoed for hours. Government artillery repeatedly pounded the central city of Homs and troops tried to storm it from three sides.

U.S. Secretary of State Hillary Rodham Clinton met with international envoy Kofi Annan in Washington to discuss how to salvage his faltering plan to end 15 months of bloodshed in Syria.