Gunfire and shelling rattled a city in central Syria on Sunday and killed a 12-year-old boy, as President Bashar Assad's autocratic regime expanded its military crackdown on a seven-week uprising by sending tanks and reinforcements to key areas, activists said.
Activists said authorities also arrested a 10-year-old boy, apparently to punish his parents, and filed charges against a leading opposition figure who is suffering from cancer.
The exact circumstances of the boy's death in the city of Homs were unclear. Like several other trouble spots, the government has answered protests there by sending in tanks and soldiers to seal it off and cutting phone service to leave it even more isolated.
The continued crackdown suggests that Assad's regime is determined to end the uprising by force and intimidation, despite rapidly escalating international outrage and a death toll that has topped 580 civilians since the unrest began in mid-March, according to rights groups.
The government disputed the civilian toll and says about 100 soldiers have been killed.
On Sunday, the state-run news agency SANA said security forces were pursuing "armed terrorist groups" in the cities of Daraa, Homs and Banias, and that six Syrian soldiers, including three officers, were killed in clashes.
The report also said 10 Syrians workers who were on their way back to Syria from Lebanon were killed in an ambush by armed terrorist groups on the Damascus-Homs highway.
The use of overwhelming force to crush an uprising worked for Syria's close ally Iran when it quelled the 2009 Green Revolution triggered by a disputed presidential election. It has also worked for the Gulf nation of Bahrain.
The U.S. has imposed sanctions on three senior Syrian officials as well as Syria's intelligence agency and Iran's Revolutionary Guard over the crackdown. The European Union is expected to impose sanctions on Syrian officials soon, and the U.N. said Saturday it is sending a team into Syria to investigate the situation.
SANA said hundreds of Syrians held a demonstration Sunday in front of the U.S. Embassy in Damascus to protest "U.S. intervention in the country's internal affairs."
The military and security forces carried out arrest sweeps and posted snipers on rooftops in flashpoints across the country Sunday, including Homs, the coastal city of Banias and the southern city of Daraa, where the uprising began, activists said.
Hundreds were arrested in Banias, including a 10-year-old boy in what appeared to be a move designed to punish the child's parents, said Rami Abdul-Rahman, director of the Syrian Observatory for Human Rights.
"Banias is a city of ghosts today, it's empty and totally isolated from the rest of Syria," said Ammar Qurabi of Syria's National Organization for Human Rights. "There's a de facto curfew and people are not going out," he said.
Qurabi also said tanks entered three villages near Daraa _ Tafas, Atman and Daael.
In Daraa, security forces allowed people to come out for few hours to buy essentials but then imposed a curfew. Thousands have been arrested.
"The prisons are full, they are now putting detainees in schools and other public buildings," he said.
Also Sunday, Qurabi said Syrian judicial authorities have formally filed charges against Riad Seif, a leading opposition figure and former lawmaker who has been an outspoken critic of the regime during the uprising.
Seif, who suffers from cancer, was charged with staging a protest without a permit. He was detained Friday, the main day for protests in the Arab world.
The nationwide uprising has posed the most serious challenge to the Assad family's 40-year ruling dynasty.
The unrest was triggered by the arrests of teenagers caught scrawling anti-government graffiti on walls in Daraa, a southern city near the border with Jordan. Despite boasts by Assad that his nation was immune from the kind of uprisings sweeping the Arab world, protests against his rule quickly spread across the country of 23 million people.
Assad, who inherited power from his father in 2000, has blamed "armed thugs" and foreigners. The regime has hit back at protesters with large-scale military operations, including an 11-day siege in Daraa that killed about 50 residents.
Syria has also banned foreign media and restricted access for reporters to many parts of the country, making it difficult to independently confirm witness accounts of the violence.
Sunday's death of the 12-year-old in Homs was confirmed by Abdul-Rahman and another activist, who declined to be named for safety reasons. The activist identified the boy as Kasem Zuhair Alahmad.
Banias, where Sunday's arrest raids were carried out, has also been sealed off. Water, electricity and nearly all forms of communication to Banias have been cut since troops in tanks and other armored vehicles rolled in on Saturday, Abdul-Rahman said.
The weekend death toll there rose to six on Sunday, Qurabi said.
Banias 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 there. 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.
Karam reported from Beirut. AP writer Elizabeth A. Kennedy contributed to this report from Beirut.