BEIRUT – U.N. observers on Friday could still smell the stench of burned corpses and saw body parts scattered around a Syrian farming hamlet where nearly 80 men, women and children were reported slain this week. 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. Western nations blame President Bashar Assad for the violent crackdown on anti-government protests that grew out of the Arab Spring.

The U.N. team was the first independent group to arrive in Mazraat al-Qubair, a village of about 160 people in central Hama province. Opposition activists and Syrian government officials blamed each other for the killings and differed about the number of dead.

Activists said that up to 78 people, including women and children, were shot, hacked and burned to death, saying pro-government militiamen known as “shabiha” were responsible. A government statement on the state-run news agency SANA said “an armed terrorist group” killed nine women and children before Hama authorities were called and killed the attackers.

Sausan Ghosheh, spokeswoman for the U.N. observers, said residents’ accounts of the mass killing were “conflicting,” and that they needed to cross check the names of the missing and dead with those supplied by nearby villagers. Mazraat al-Qubair itself was “empty of the local inhabitants,” she said.

She told the BBC: “We can say that there was definitely a horrific crime that was committed. The scale is still not clear to me.”

A BBC correspondent traveling with the U.N. observers described the hamlet as an “appalling scene” of burned-out houses and gore.

“They killed the people, they killed the livestock, they left nothing in the village alive,” said the correspondent, Paul Danahar.

The United States condemned Assad over the killings, saying he has “doubled down on his brutality and duplicity.”

The violence followed another mass killing last month in a string of villages known as Houla, where 100 people including many women and children were also shot and stabbed to death. The opposition and the regime blamed each other for the Houla massacre.

In April, the U.N. said more than 9,000 people have been killed since the crisis began in March 2011, but it has been unable to update its estimate since and the daily bloodshed has continued in past weeks. Activists put the number of dead at about 13,000.

Before her meeting with Annan, Clinton said they would look at “how to engender greater response by the government of Syria to the six-point plan that he has put forth.”

Annan’s plan calls for an end to violence followed by a political transition. Although Assad agreed to it, the violence has continued unabated with reports of brutal massacres against innocents.

Annan allowed that some people “say the plan is definitely dead.” He asked rhetorically whether the problem is the plan or its implementation.

“If it’s implementation, how do we get action on that? And if it’s the plan, what other options do we have?” he said.

U.N. diplomats say Annan is proposing that world powers and key regional players, including Iran, come up with a new strategy to end the conflict.