Baghdad governor Ali al-Haidri was assassinated by gunmen in the capital Tuesday, report Al Jazeera and other agencies quoting police and hospital sources.

The details remain unclear.

Also on Tuesday, a truck bomb exploded at a police post near an entrance to the fortified Green Zone complex in Baghdad, killing at least 13 people and wounding at least 28.

Haidri, who survived a previous assassination attempt in September, is the most senior Iraqi official to be killed in Baghdad since the head of the Governing Council was killed by a suicide bomb in May last year.

Armed fighters have repeatedly targeted Iraqi officials as well as the security forces as part of their  effort to destabilise the US-backed interim government.

The blast at the entrance to the Green Zone--which houses government offices and embassies -- followed at least two car bomb attacks in the capital on Monday. One of the attacks killed two policemen and a civilian near interim Prime Minister Iyad Allawi's party headquarters.

Three British nationals were also killed in a Baghdad explosion on Monday, the British Foreign Office said.

Separately, a US marine was killed in action in al-Anbar province, west of Baghdad, on Tuesday, the US military said, giving no further details. Al-Anbar province includes the cities of Ramadi and Falluja, where US forces launched a major assault in November.

Since the invasion to oust Saddam Hussein in March last year, at least 1049 US military and Pentagon personnel have been killed in action in Iraq. Including non-combat deaths, the toll is now at least 1334.