A Foreign Office spokesman said: “We are aware of the tragic death of a Briton in Libya and we stand ready to provide consular assistance.”
It is believed the victim’s family is not aware of his death.
A woman from New Zealand has also been reported killed. A Libyan security source said that the bodies were found near the coastal area of Mellitah in western Libya.
The killings come a month after a US teacher was shot dead in the eastern city of Benghazi, after which the Foreign Office said further attacks against Westerners were likely.
Mellitah is near the town of Zuwarah, 60 miles west of Tripoli, and is home to a large oil and gas complex co-owned by Italian company ENI.