Syrian troops fired bullets and tear gas to disperse thousands of protesters Friday, activists said, and state media reported that a roadside bomb killed 10 soldiers in the latest violence to defy international efforts to calm the country's crisis.

Protesters spilled out from mosques onto the streets in cities and towns across Syria, calling for the downfall of President Bashar Assad and chanting in support of the country's rebel forces, activists said.

A cease-fire that technically went into effect last week has been steadily unraveling, but the truce is still seen as the most viable way to end the bloodshed that has killed more than 9,000 people since the uprising against Assad began 13 months ago. The U.N. has sent a team of seven international observers into Syria, with the hopes of boosting the numbers soon.

U.S. Secretary of State Hillary Rodham Clinton called Thursday for the U.N. Security Council to adopt an arms embargo and other tough measures against Syria. And U.N. Secretary-General Ban Ki-moon took a hard line against Damascus, saying Syria was not honoring the cease-fire and that violence was escalating.

On Friday, protests were reported in the capital Damascus and its suburbs, as well as in the northern city of Aleppo, the central regions of Hama and Homs, in eastern towns near the border with Iraq and in the southern Daraa province.

"Security is extremely tight in Damascus," said activist Maath al-Shami, adding that despite the wide presence of plainclothes security agents, there were protests in the capital's neighborhoods of Qaboun, Midan, Barzeh and Mazzeh.

He said troops opened fire into the air to disperse the protesters. Activists also said that troops opened fire at protesters in Aleppo, Syria's largest city, as well as the central city of Hama. They had no immediate word on casualties.

In the rebel-held Khaldiyeh neighborhood in the central city of Homs, a mortar round was hitting every five minutes, according to the Britain-based Syrian Observatory for Human Rights. An amateur video posted online by activists showed thick black smoke billowing as shells fell in a residential area.

Citing its network of sources on the ground, the group said explosions and cracks of gunfire rang out in the town of Qusair, near the border with Lebanon. Activists said regime forces were sending reinforcements to Qusair.

"Regime forces are fortifying their positions in eastern and western Qusair," about 10 kilometers (7 miles) from Lebanon, said the head of the Observatory, Rami Abdul-Rahman.

Meanwhile Syria's state-run news agency SANA said a large roadside bomb went off in the southern village of Sahm al-Golan, near the Israeli-occupied Golan Heights, killing 10 soldiers. It gave no further details.

In Paris, France's Foreign Minister Alain Juppe said Friday that the international community has to live up to its responsibilities in Syria and prepare for the possible failure of an increasingly fragile peace plan. He told France's BFM television that if special envoy Kofi Annan's peace plan "doesn't function, we have to envisage other methods."

Clinton had referred during the Paris meeting to a resolution under the U.N. Charter that would be militarily enforceable.

"We need to start moving very vigorously in the Security Council for a Chapter 7 sanctions resolution, including travel, financial sanctions, an arms embargo, and the pressure that that will give us on the regime to push for compliance with Kofi Annan's six-point plan," she said.

Her comments were welcomed by the Syrian opposition.

"The fact that Mrs. Clinton talked about this resolution (Chapter 7) shows that the international community is preparing to take stronger action against this cruel regime," said Fawaz Zakri, an Istanbul-based member of the Syrian National Council.

Ban has recommended the Security Council quickly approve a 300-member U.N. observer mission to Syria, a number larger than what was originally envisioned. But he said he will review ground developments before deciding when to deploy the mission.

Ahmad Fawzi, a spokesman for international Syria envoy Kofi Annan told reporters in Geneva Friday that the United Nations hopes to have 30 cease-fire monitors in the country next week.

An amateur video posted online by activists showed the head of the observer team, Col. Ahmed Himiche, talking to residents in the southern town of Khirbet Ghazaleh on Thursday. Himiche asked them whether schools and hospitals are available in the town.

"They (troops) assassinate whoever we take to the general hospital," one man replied.

A woman told him that she was desperately seeking information on her missing sons.

"My two sons, who are farmers, were taken three months ago and I don't know anything about what happened to them," she said. She picked up her grandson and brought him to Himiche, instructing the child to say: "I want my father."