Gunfire erupted Wednesday as U.N. observers drove through an anti-regime demonstration in a Damascus suburb, sending people ducking for cover and raising questions about the safety of the monitors, according to activists and amateur video posted online.

The videos could not be independently confirmed. But the Britain-based activist group Syrian Observatory for Human Rights said Syrian security forces fired at anti-regime protesters in the suburb of Arbeen, wounding eight.

Under a plan brokered by U.N.-Arab League envoy Kofi Annan, six observers arrived in Syria over the weekend as an advance team for a larger contingent meant to shore up a week-old cease-fire that has been buckling under regime assaults on opposition strongholds and several bombings and shootings by the rebels. The truce was supposed to pave the way for talks between Assad and the opposition trying to topple him.

Annan's spokesman, Ahmad Fazwi, confirmed that the U.N. observers were in Arbeen on Wednesday. He said it would be "appalling" if it was confirmed Syrian forces opened fire in the area.

Annan's plan is seen as a last hope for reversing Syria's slide toward civil war after a 13-month-old uprising to oust President Bashar Assad killed more than 9,000 people, according to the U.N.

Despite persistent violence, the international community is reluctant to declare the cease-fire dead, in part because it is seen as the only way to end bloodshed in Syria. Other options, such as foreign military intervention, arming Assad's opponents and economic sanctions, have either been discarded or offer no quick solution. A deadlocked international community would be hard put to offer an alternative if it were to acknowledge the collapse of the truce.

Ban Ki-moon, the U.N. chief, is expected to send a letter to the U.N. Security Council later on Wednesday to report on Syrian compliance with the truce, something that will help determine whether conditions are right to expand the observer mission.

In Arbeen, several thousand anti-regime protesters took to the streets, said Rami Abdul-Rahman, head of the Observatory. At one point, security forces opened fire, wounding eight demonstrators, he said.

In amateur videos said to show the events in Arbeen, hundreds of demonstrators are seen crowding around at least three U.N. vehicles, clapping, waving Syrian flags and chanting in support of the rebel Free Syrian Army. A handwritten sign taped to one of the U.N. cars, apparently by the protesters, reads: "The butcher keeps killing, the observers keep observing and the people keep up the revolution."

Another video shows hundreds walking along as the two U.N. vehicles slowly make their way through a wide street in Arbeen. When a shot rings out, the two U.N. cars speed away, leaving the demonstrators behind.

In a third video posted online by the same user, hundreds of people waving flags are seen in a march. Suddenly, they panic and run for cover. A narrator says they are being shot at while the observers are in the area and gunfire is heard in the background.

Syrian Foreign Minister Walid Moallem promised that the regime would respect the cease-fire and withdraw troops from urban centers in line with Annan's peace plan. However, the regime has so far ignored last week's deadline to get tanks and troops off the streets.

Instead, Syrian soldiers continued to pound rebellious areas with artillery after an initial lull of about one day at the start the truce. The ongoing attacks have dimmed hopes for Annan's plan.

Activists said regime forces fired mortar shells again at the central city of Homs, killing at least two civilians and sending thick gray smoke into the air as loud booms rang across residential areas. Homs has been battered by artillery for weeks, with just a brief respite at the start of the cease-fire.

The state news agency said two separate roadside bombs killed 10 members of the security forces and a civilian in northern Syria. SANA reported that six soldiers were killed and 11 wounded in a blast in the village of Mastouma in Idlib province, while a second explosion in the Aleppo region killed four members of the security forces and a civilian.

The attacks were a sign that both sides have violated the cease-fire and could prompt the regime to intensify its assault on rebellious areas. Syria's government has portrayed the uprising as a foreign-led conspiracy by terrorists and thugs.

Still Moallem insisted Syria is keeping its commitments. Syria will "continue to cooperate" with Annan's efforts, the Chinese Foreign Ministry quoted Moallem as saying after he met with his Chinese counterpart in Beijing.

Syria will "honor and implement Annan's six-point proposal, fulfill its cease-fire, troop withdrawal and other relevant commitments and begin cooperation with the U.N. monitoring team," Moallem said according to the statement.

China, Russia and Iran have been Syria's staunchest allies. U.N. Security Council members Russia and China have twice shielded the Assad regime from international condemnation, but also demanded that Syria comply with the Annan plan.

After Russian Foreign Minister Sergey Lavrov told Moallem last week that Syria could do better, his Chinese counterpart, Yang Jiechi, urged his Syrian visitor Wednesday to make the Annan plan work.

Yang said he hoped Syria would "actively cooperate in putting in place the cease-fire monitoring mechanism, and sincerely embark on a process of inclusive political dialogue and reform to bring about a just, peaceful, and appropriate resolution to the Syrian question."

Yang's remarks were more pointed than in past, an indication that Beijing is looking for progress toward a reduction of violence that might dilute some of the criticism China has come under for blocking U.N. action on Syria.

Meanwhile, Ban, the U.N. chief, is intensifying efforts to get a large contingent of observers on the ground to salvage the truce. He said a team of 250 monitors, as originally envisioned, might not be sufficient for the job. He has also asked the European Union for planes and helicopters to make the mission more effective.

Moallem said in Beijing that Syria would be ready to provide helicopters, but made no reference to Ban's request to the EU.

"Syria is ready to make its air force available for the use of this delegation," Moallem said. "As we have understood, what is needed are helicopters to evacuate the injured. If that is the issue, then we have the capabilities in our air force to carry this out."


Associated Press writer Scott A. McDonald in Beijing contributed reporting.

(This version CORRECTS Adds details, video, corrects that U.N. chief is sending a letter to the Security Council instead of briefing)