Syrian forces have shelled the central city of Hama killing close to 30 and leaving scores injured according to activists.
Hama is a crucible of anti-Assad sentiment.
Witnesses say the shelling started then, security forces moved in shooting and torching houses.
The Syrian government has yet to comment. It claims to be committed to the April 12 ceasefire, but reserves the right to respond to what it calls “terrorist attacks”.
The incident happened a day after UN observers visited the city.
The United Nations has announced that a further 300 monitors are to be sent to the country by next week.