Syrian tanks and troops enter Baniyas

According to internet reports that are surfacing fast, Syrian tanks entered the city in three places in the early hours of Saturday and were heading towards the Sunni districts of the coastal city.

The information was relayed to news agencies by human rights activists in the field. The BBC reports that they have been unable to confirm the reports as communications to the city appeared to have been cut.

They said the armed units were advancing on the Sunni Muslim areas of the city from three directions - steering clear of neighbourhoods of the minority Alawite sect, to which the president and his family belong.

"Residents are reporting the sound of heavy gunfire and seeing Syrian navy boats off the Baniyas coast. Sunni and mixed neighbourhoods are totally besieged now," one anonymous rights campaigner told Reuters.

The AFP news agency reported that protesters had formed human chains to try to stop the military operation.

Many feared the city - which has witnessed some of the most persistent demonstrations - would come under siege like Deraa in the south where the uprising erupted seven weeks ago.

The Damascus Center for Human Rights Studies (DCHRS) accused the government of carrying out "10 days of massacres" as it attempted to take back Deraa.

The US has warned Damascus to end its brutal crackdown on protesters.

The White House said on Friday it would take "additional steps" if President Bashar al-Assad did not take steps to end the bloodshed.

More than 500 people are thought to have been killed in the uprising since mid-March.

At least 21 people were reportedly killed in Homs, Hama and other cities on Friday, in what protesters had vowed would be a "day of defiance".

No reports can be verified independently, as foreign journalists are not allowed into Syria.