Time for Assad to go - British Prime Minister David Cameron
19 July 2012 Last updated at 09:43 BST
There have been clashes throughout the night in many parts of Syria, after the deaths on Wednesday of three top regime figures in a suspected suicide attack.
The president's brother-in-law, defence minister and head of Mr Assad's crisis team died in the bombing.
David Cameron said Mr Assad should step down and that it was "time for transition in this regime".