An Iranian diplomat was assassinated in Baghdad on Thursday as gunmen opened fire on his car near the Iranian mission, the Qatar-based al-Jazeera TV channel reported.

The diplomat identified by the Iranian state TV as the first secretary of Iran's embassy in Baghdad, Khalil Naimi, was shot dead close to Tehran's diplomatic mission in Baghdad.

He was attacked by three unknown gunmen when he was driving on his way to the embassy.

The motive of the killing was still unknown.

An Iranian delegation has been in Iraq to help mediation between the US-led authorities and Shiite cleric Moqtada al-Sadr.

The United States has vowed to kill or capture Sadr and destroy his militia, but both sides have said they prefer to avoid bloodshed.