Troops and tanks are reported to have swept into the Syrian city of Baniyas

Troops and tanks are reported to have swept into the Syrian city of Baniyas, a centre of anti-government protests.

They entered in three places and were heading towards the Sunni districts of the coastal city, human rights activists told news agencies.

The BBC's Jim Muir in neighbouring Lebanon said he had been unable to confirm the reports as communications to the city appeared to have been cut.

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.

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