Updated

A 12-year-old boy was killed Sunday as gunfire and shelling erupted in the central Syrian city of Homs, a flashpoint in the widespread seven-week-old uprising against President Bashar Assad's autocratic regime, an activist said.

The death coincided with a major crackdown in the coastal city of Banias, another protest hotbed where activists reported the arrest of more than 200 people — including a 10-year-old boy.

"It appears to be designed to punish his parents," said Rami Abdul-Rahman, director of the Syrian Observatory for Human Rights.

He said water, electricity and nearly all forms of communication to Banias have been cut since troops in tanks and armored vehicles rolled in and sealed off the city on Saturday. According to another activist, who declined to be named for fear of reprisal, the two-day death toll in Banias had risen to six.

The nationwide uprising has posed the most serious challenge to the Assad family's 40-year ruling dynasty. Bashar Assad, who inherited power from his father in 2000, is expanding a campaign of violence and arrests aimed at crushing the revolt even as international condemnation intensifies.

More than 580 civilians and 100 soldiers have been killed since the revolt began, rights groups say.

The events in Banias came on the heels of a large-scale military operation in the southern city off Daraa. About 50 residents were killed in an 11-day siege there.

Syria has banned foreign media and restricted access for reporters to many parts of the country, making it difficult to confirm witness accounts independently.

Homs, like several other trouble spots, is sealed off by tanks and soldiers, and telephone service has been cut. The activist who reported the death of the 12-year-old there has proven reliable with past reports.

The uprising was sparked in mid-March by the arrest of teenagers who scrawled anti-regime graffiti on a wall in Daraa. Protests spread quickly across the nation of some 23 million people, inspired by uprisings sweeping the Arab world.

Banias — target of the latest crackdown — has a large power station and one of the country's two oil refineries and is the main point of export for Syrian oil. It is predominantly Sunni Muslim but also is home to many Alawites — the sect of the ruling Assad family and many senior officials.

Syrian officials and state-run media have tried to portray Banias as a hotbed of Islamic extremists to justify the crackdown. The state news agency SANA said the army and security forces were pursuing fugitives in Banias and were able to arrest a large number of them and confiscate their weapons.

On Sunday, SANA said Syrian authorities have seized sophisticated weapons and that the army is still hunting down "armed terrorist groups" across the country, including in Banias.

The U.S. has imposed sanctions on three top Syrian officials as well as Syria's intelligence agency and Iran's Revolutionary Guard over the crackdown. The European Union is expected to place sanctions on Syrian officials soon, and the U.N. said Saturday it is sending a team into Syria to investigate the situation.