Britain's Prime Minister David Cameron joined the chorus of tributes to the respected Sunday Times journalist Marie Colvin who was killed by a rocket attack in Syria.

Cameron described Colvin as "talented" to the House of Commons during Prime Minister's Questions.

"This is a desperately sad reminder of the risks that journalists take to inform the world of what is happening and the dreadful events in Syria, and our thoughts should be with her family and with her friends," Cameron said.

US-born Colvin died in the Syrian city of Homs during a shelling by President Bashar al-Assad's forces.

She was the only British journalist in the city.

Her last report from the trouble in Syria, which has seen despot Assad use his armed forces to kill hundreds of men, women, and children in a desperate bid to assert his authority, painted a stark picture of Homs.

"Almost every building is pock-marked after tank rounds punched through concrete walls or rockets blasted gaping holes in upper floors," she wrote.

"The building I was staying in lost its upper floor to a rocket last Wednesday. On some streets whole buildings have collapsed - all there is to see are shredded clothes, broken pots and the shattered furniture of families destroyed.

"The scale of human tragedy in the city is immense. The inhabitants are living in terror."

People flocked to Twitter to share their tributes to Colvin.

"Terrible, terrible news about Marie Colvin, killed in Homs this morning. Amazing woman, will be missed by everyone who worked with her," tweeted Andrew Wander, emergencies media manager for Save the Children.

Colvin won several awards in her career, including the prestigious Martha Gelhorn Prize in 2009.

A 28-year-old French photographer called Remi Ochlik also died in the attack.