Syria: Security forces enter Homs to crush protests
Syrian security forces have moved into parts of the city of Homs, a centre of the nationwide protests against President Bashar al-Assad.
There were reports of heavy shooting in the city - rights groups said a 12-year-old boy had died.
State media said several "armed saboteurs" had been killed or wounded, arrests made and quantities of arms and ammunition seized.
Police operations are also continuing in Baniyas and Deraa.
The Sana state news agency reported that 10 civilian workers travelling to Homs from Lebanon had been killed in an ambush by an armed gang.
Some 15 people were shot dead in Homs on Friday as they staged demonstrations after weekly prayers.
The authorities say 11 soldiers and police were also killed, blaming "armed terrorist groups" for the violence.
On Sunday night, troops and police moved into Homs with tanks, said Syrian state TV, confirming reports from activists and residents.
Heavy machine-gun fire and shelling were heard on the streets. Activists said a 12-year-old boy was killed but the circumstances of his death were not clear.
Electricity and communications to the city of one million people were cut before the operation began - a technique which the security forces have used before in other cities.
Foreign journalists are banned from entering Syria, so reports are difficult to independently verify.
In the coastal city of Baniyas, activists say six people were shot dead on Friday night and at least 200 people - including a 10-year-old boy - arrested.
"It appears to be designed to punish his parents," said Rami Abdul-Rahman, director of the UK-based Syrian Observatory for Human Rights.
He told reporters that snipers had taken up position on rooftops in the southern districts.
In Deraa, the southern city where the unrest began in March, residents also remain cut off from the rest of the country.
Scores of people have been killed in Deraa during a 10-day security operation.
Meanwhile, the authorities have filed charges against prominent opposition politician Riad Seif.
Mr Seif, who suffers from cancer, was arrested on Friday accused of staging a protest without a permit.
Across Syria, demonstrators have been calling for greater political rights and personal freedoms. Some are calling for the downfall of the regime.
The unrest in Syria poses the most serious challenge to Mr Assad since he succeeded his father, Hafez, in 2000.
On Friday, the US said the violence against protesters was "deplorable" and pledged a "strong international response" against Syria's government if Damascus does not end its brutal crackdown.
More than 500 people are thought to have been killed since mid-March.
A mobile phone snapshot, reportedly taken in Qamishli on 29 April, shows protesters carrying banners written in Arabic and Kurdish demanding democracy.
Razan, who is a resident of Damascus, tells the BBC about violence and protests around Syria.
This unverified video seems to show a peaceful protest in Talbisah. Moments into the footage, tanks fire on unarmed civilians. Wyre Davis reports.
Residents of Deraa walk past a burnt-out building. It follows shelling by troops in what human rights groups say was an intensified crackdown on protests in recent weeks.
Syrian army vehicles were photographed near Homs and broadcast on the Syrian opposition internet channel Sham SNN on 11 May.