At least six people have been reported dead after the Syrian military carried out raids on a restive city in the west of the country.
Tanks and soldiers surrounded Hama after some of the biggest demonstrations yet against the rule of President Bashar al-Assad.
Residents are reported to have tried to stop the advance of military convoys by blocking roads with rubbish containers and burning tyres and wood.
Hama is the latest in a string of towns and cities where anti-government protesters have taken to the streets, provoking an angry response from Assad.
France is urging the UN to stand up to what it calls unacceptable and ferocious armed repression.
Rights groups estimate that 1,300 civilians have been shot and killed by security forces since demonstrations began in March.
Some 12,000 people are reported to have been arrested.
Authorities claim gunmen are mostly to blame for the civilian deaths, and accuse them of killing around 500 police and soldiers.