United Nations observers made it to the site of an alleged massacre Friday after they were blocked access the day before, a Syrian activist said.

The U.N. team was shown burned houses and graves of the victims in the village of Qubeir, activist Mousab Alhamadee told CNN.

At least 78 people were killed in Qubeir, according to the opposition network Local Coordination Committees (LCC) of Syria.

A video of the carnage was posted on YouTube. CNN could not independently verify its authenticity.

Opposition activists said government forces shelled Qubeir for an hour before militias on foot turned AK-47 rifles on people, some at close range, or slashed them with knives. Some residents suspected the Shabiha, armed gangs that work as freelancers for the government.

Qubeir resident Laith Al-Hamawy said he showed the U.N. monitors the aftermath of shelling by Syrian forces. He then fled the area, he said, because the military threatened death to residents who approached the U.N. team.

The Syrian government blamed terrorists for the attack in Qubeir and said nine people were killed.

Graphic images of the Qubeir massacre sparked strong condemnation for Syrian President Bashar al-Assad, who international leaders said has failed to abide by a peace plan brokered by Kofi Annan, a special envoy on Syria for the United Nations and the Arab League.

Annan was meeting Friday with U.S. Secretary of State Hillary Clinton after a marathon session on Syria in the U.N. General Assembly the day before.

He said he will discuss with Clinton how to ratchet up pressure on al-Assad to change his course of action and what other options the international community has in terms of halting the bloodshed.

Al-Assad is accused of engineering a bloody crackdown to suppress a 15-month anti-government uprising.

“Syria is a real, real challenge,” Annan said.

Also Friday, China condemned the ongoing violence in Syria, while throughout the embattled country, warplanes flew overhead and the sounds of explosions and gunfire echoed as protesters gathered for another round of demonstrations.

Using some of the strongest language to emerge from Beijing on the violence in Syria, Foreign Ministry spokesman Liu Weimin called for an immediate end to the violence, including massacres that have left hundreds of people — including women and children — dead.

“We strongly condemn the recent brutality on women and children,” he said. “We call for a punishment of the murderer.”

While Liu said China “holds an open attitude towards any solution that would help ease the situation in Syria and possibly push forward a political solution,” there was no indication that Beijing had changed its position on outside intervention in Syria.

On Thursday, Chinese President Hu Jintao signed a joint declaration with Russia and four Central Asian nations rejecting armed intervention or efforts to topple al-Assad’s regime.

Instead, they reiterated support for Annan’s mediation efforts and called on all parties in the conflict to stop violence and engage in dialogue.

Frustrated world leaders warned that Syria is engaging in crimes against humanity and drifting closer to civil war.

“How many more times have we to condemn them, and how many ways must we say we are outraged?” U.N. Secretary-General Ban Ki-moon said Thursday after 10 hours of talks on Syria. “The danger of full-scale civil war is imminent and real, with catastrophic consequences for Syria and the region.”

Diplomats echoed a sense of urgency to end escalating bloodshed.

“Enough is enough,” Arab League chief Nabil el-Araby said as he called for “all kinds of pressure” on Damascus.

A delegation denied entry into Syria last week interviewed witnesses in neighboring countries who described torture, threats and horrific attacks, according to a top U.N. official.

“There is unselective shelling, there is deliberate targeting with live munition of protesters, there is systematic torture going on in prisons,” said Ivan Simonovic, the U.N. assistant secretary-general for human rights.

Simonovic said the torture involved, among other things, rape and the use of fire.

“It’s appalling,” he said.

On Friday, government forces swarmed mosques and neighborhoods in Damascus as warplanes flew overhead, according to the Local Coordination Committees.

Large demonstrations were taking place in Damascus, Aleppo, Idlib and Deir Ezzor as government forces fired on protesters with bullets and tear gas, setting fire to cars and killing at least four, according to the LCC.

One of the dead was a child shot in the head by a sniper, the group said.

The LCC said government forces were shelling Haffah, in Lattakia province, and the army was trying to storm the village. The group said there were explosions throughout Halfaya, in Hama province.

Opposition activists also reported a series of attacks Friday, including an explosion at a police station that left five dead and a civilian killed when regime forces at a checkpoint opened fire on his car.

In a separate attack, a bus blast killed two regime soldiers in a suburb of Damascus Countryside province, the Syrian Observatory for Human Rights said. Syrian state TV said two civilians were killed in that attack.

The state-run news agency, SANA, reported an attack on oil installations in Deir Ezzor that left one soldier dead, as well the deaths of two police officers and three civilians in a car bomb explosion in Idlib.

SANA also reported the seizure of “large amounts of modern and advanced weapons” from a vehicle coming from Lebanon. The weapons reportedly included U.S.-made sniper rifles, heavy machine guns from Israel, detonators and French-made missiles.

It was unclear if those incidents occurred Friday.

CNN cannot independently confirm reports from within Syria because the government limits access by international journalists.

Annan called the situation dire.

“You could say we are drifting, if we are not already in, a sort of a civil war,” he said. “All efforts are being made that, if it were to become a full-blown civil war, it doesn’t spread to neighbors.”

In April, Annan brokered a peace plan in Syria that included calls for warring sides to silence their guns and lay down their weapons. But provisions in the plan have not been met, and the most visible evidence is the continuing bloodshed.

Ban said there is minimal evidence that the regime is complying with its commitment under the Annan plan, saying the opposition “is hardening and turning increasingly to arms.”

Killings in recent weeks may amount to crimes against humanity, he said.

Opposition groups estimate that 12,000 to at least 14,000 people have been killed in the Syrian uprising. Tens of thousands of others have been displaced.

A planned June 20 summit in Mexico will include discussions on how to proceed, Ban said.

— CNN’s Saad Abedine, Hamdi Alkhshali and Moni Basu contributed to this report.