Amateur video posted on the internet captures what is purported to be one of the latest attacks by Syrian forces on the besieged city of Homs.
Explosions are heard and smoke can be seen rising over buildings.
Two western journalists were killed in Homs earlier this week, including Sunday Times correspondent Marie Colvin.
““Marie Colvin was an absolute giant as a foreign correspondent,” British Prime Minister David Cameron said on Thursday.
“What has happened there is I believe not just a tragedy, but I think it’s right to see this as yet another evil act by the Syrian government,” he added.
British photographer Paul Conroy and two others were wounded in the same attack that claimed Marie Colvin’s life.
Video uploaded to the web apparently shows him appealing for international help. Medics from the Free Syrian Army are said to be treating him.