Syrian forces reportedly shelled the port of Latakia for the third consecutive day on Monday.
Anti-government activists posted amateur footage which they said showed tanks patrolling the city.
The number of casualties was unknown.
On Sunday, Damascus denied that any shelling had taken place.
The opposition also says the military has again fired on protesters in Homs, Syria’s third-largest city.
Government officials say troops are tackling ‘armed gangs’ — protesters against President Bashar al-Assad’s rule deny that claim.
Reports from Syria are impossible to verify as foreign journalists are banned from the country.
More than 1,700 people are said to have died in the six-month uprising.
Al-Assad’s regime has come under intense diplomatic pressure to end the violence.
But the Syrian government vows there will be no letup in the crackdown on protests and accuses the West of interfering in its domestic affairs.