Opposition activists and witnesses said that Colvin - an American reporter working for the British newspaper - and photographer Remi Ochlik lost their lives after the makeshift media centre where they were staying was shelled, reports the AFP news agency.
Reuters said that the two war correspondents were killed by a rocket after they tried to escape the building in Baba Amr district.
Activists claimed that more than 40 people died in the attack on Tuesday, including Rami al-Sayed, a man whose live video stream broadcasts from Homs were often used by the global media.
Colvin, who was known for wearing a black eye patch due to a shrapnel wound received while covering the civil war in Sir Lanka in 2001, was thought to be the only British newspaper journalist working amid the violence in Homs.
At least two other Western journalists, including British photographer Paul Conroy, were thought to have been wounded yesterday after in excess of ten rockets hit the house. They are understood to be in a serious condition.
Before the attack yesterday, Colvin presented a video for the BBC and CNN detailing the "absolutely sickening" bloodshed in the Syrian city. She said that she had seen a "little baby" die in the "horrific" violence.
Colvin previously said in a piece in the Sunday Times that the citizens in Homs were "waiting for a massacre".
"The scale of human tragedy in the city is immense," she wrote. "The inhabitants are living in terror. Almost every family seems to have suffered the death or injury of a loved one."
Born in France in 1983, Remi Ochlik covered his first conflict in Haiti at the age of 20 and had more recently photographed revolutions in Tunisia, Egypt and Libya.
French television reporter Gilles Jacquier was killed in Homs last month after a shell exploded close to him as he covered protests in the city on a visit organised by the Syrian government.
Last week, tributes poured in to New York Times reporter Anthony Shadid after he died of an asthma attack while trying to reach the opposition zone in Syria.
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