He and his Iraqi translator had been abducted at gunpoint hours earlier, according to police, and his death was confirmed by the US embassy.
“I can confirm to you that officials in Basra have recovered the body of journalist Steven Vincent,” said embassy spokesman Pete Mitchell, speaking to the Associated Press.
“The US embassy is working with British military and local Iraqi officials in Basra to determine who is responsible for the death of this journalist. Our condolences go out to the family.”
Steven Vincent’s death comes four days after an opinion piece he wrote criticising the rise of Shi’ite Islamist fundamentalism in Basra was published in The New York Times.
Iraqi police in Basra said the pair was seized by five gunmen in a police car as they left a currency exchange shop on Tuesday evening.
His body was discovered on the side of the highway south of Basra, with multiple shots to his head and body.
His translator was shot four times and was seriously wounded, according to police.
Vincent was the author of a book on post-war Iraq and was researching another about Basra’s history.
In his August 1 New York Times article, he criticised British forces for failing to clamp down on Shi’ite religious groups.
He also quoted an Iraqi police officer who said some police have been behind many of the assassinations of former Baath Party members in the southern city.
“He told me that there is even a sort of ‘death car’: a white Toyota Mark II that glides through the city streets, carrying off-duty police officers in the pay of extremist religious groups to their next assignment,” he wrote.
Basra has suffered relatively few suicide bombings and assassinations, unlike other parts of Iraq.
However residents have reported that Shi’ite fundamentalists have been gaining increasing control over the city.