Beirut: Syrian troops stormed and shelled districts in a suburb of the capital Damascus on Sunday, activists said, a day after the Security Council voted to expand the number of UN truce monitors from 30 to 300 in hopes of salvaging an international peace plan marred by continued fighting between the military and rebels.

An eight-member team is already on the ground in Syria, and since Thursday has visited flashpoints of the 13-month-long conflict. Fighting generally temporarily stops when the observers visit an area, but there has been a steady stream of reports of violence from towns and regions where they have not yet gone.

"This UN observers thing is a big joke," said Mohammed Saeed, an activist in the sprawling Damascus suburb of Douma, which came under fire from regime troops today. "Shelling stops and tanks are hidden when they visit somewhere, and when they leave, shelling resumes."

His comments reflect a widespread lack of faith among many Syrians in international envoy Kofi Annan's cease-fire plan for ending the violence in Syria and launching talks between President Bashar Assad and those trying to oust him.

Syria's opposition and its Western supporters suspect Assad is largely paying lip service to the truce since full compliance, including withdrawing troops and heavy weapons from populated areas and allowing peaceful demonstrations, could quickly sweep him from power.

So far, the regime has kept up its attacks on opposition strongholds, though on a smaller scale than before the truce deadline.

Saeed said two people were killed today by indiscriminate firing in Douma, which was the scene of intense clashes between rebels and security forces before the UN-brokered cease-fire went into effect more than a week ago.

The Syrian Observatory for Human Rights, a Britain-based opposition group with a network of activists on the ground, confirmed the deaths. It said four soldiers were also killed when a roadside bomb hit an armoured personnel carrier in the town later on Sunday.

The Observatory also reported that security forces killed three people in the northern province of Idlib and one person in the village of Hteita outside Damascus when troops opened fire from a checkpoint.

It was not immediately clear what prompted the attack on Douma. Saeed said loud explosions that shook the city early on Sunday caused panic among residents, some of whom used mosque loudspeakers to urge people to take cover in basements and in lower floors of apartment buildings.