BEIRUT - Syrian security forces fired on antigovernment demonstrations across the country Friday, killing at least 24 people - including several children - as the regime tries to choke off a nine-month-old uprising, activists said.

Some of the worst violence was reported in the central Syrian city of Homs, which has emerged as the epicenter of the revolt against President Bashar al-Assad.

"The earth was shaking," a Homs resident said by telephone of explosions and cracks of gunfire that erupted in the early morning. "Armored personnel carriers drove through the streets and opened fire randomly with heavy machine guns." He spoke on condition of anonymity for fear of retribution.

Despite the relentless bloodshed, Assad has refused to buckle to the pressure to step down and shown no signs of easing his crackdown. The U.N. says more than 4,000 people have been killed in the military assault on dissent since March.

Two boys, ages 10 and 12, were hit by stray bullets Friday near government checkpoints in Homs, according to activists. At least two other young teenagers were killed elsewhere, the activists said.

Rami Abdul-Rahman, head of the British-based Syrian Observatory for Human Rights, said the 10-year-old was shot as he crossed the street in the Bab Sbaaa neighborhood. The 12-year-old was struck as he walked in a crowd exiting a mosque, Abdul-Rahman said.

Antigovernment demonstrations traditionally peak after Friday's midday prayers, though witnesses say there appeared to be a concerted effort to prevent gatherings this week. Troops were deployed heavily and, in many cases, they locked down areas before prayers even began.

Security forces also reportedly fired on protests in the Damascus suburbs, the eastern city of Deir el-Zour, Idlbi province near Turkey, and elsewhere.

In the southern town of Daraa, activists said phone and Internet lines were cut.

An activist coalition called the Local Coordinating Committees said that up to 35 were killed Friday, most of them in Homs. The Britain-based Observatory had a death count of 24. Casualty tolls are difficult to compile in Syria, where the government has prevented independent reporting and where violence often prevents activists from counting the dead.

In Lebanon, Bomb Hits U.N. Soldiers

A roadside bomb struck a vehicle carrying U.N. peacekeepers Friday in southern Lebanon, wounding five French soldiers and a Lebanese bystander, officials said.

It was the third bombing this year targeting the international force known as UNIFIL, which is deployed to keep the peace along Lebanon's border with Israel. No group has claimed to be behind the attacks.

The blast comes amid fears that violence in neighboring Syria might spread into Lebanon, which was dominated by Damascus for three decades until Syrian troops withdrew in 2005.

French Foreign Minister Alain Juppe called on Lebanese authorities to bring those responsible to justice and to guarantee the security of the peacekeepers.

- Associated Press