A car bomb hit a private security convoy in Baghdad on Thursday, killing four people and wounding at least nine others, security and medical officials said.

The bomb exploded in the Mansur area of west Baghdad about 9:00 am (0600 GMT), killing four people and wounding nine, an interior ministry official said.

A medical source from Al-Yarmuk hospital confirmed the facility had received four bodies, but put the number of wounded at 14.

It was not immediately clear whether the casualties were bystanders, people travelling the convoy, or both. Neither official gave details on the name of the security company.

Private security firms in Iraq have faced difficulties in obtaining visas and various licences since United States forces withdrew from Iraq at the end of last year.

Iraq deeply mistrusts security companies over perceived arrogant behaviour by employees of the firms in the past and various incidents of violence involving them.

The most infamous such incident was the 2007 killing of at least 14 civilians in Baghdad's Nisur Square by gunmen from the Blackwater firm guarding a US embassy convoy.

While Blackwater, now called Academi, was later banned from the country, a number of other private security firms still guard diplomats in Iraq and provide security for various foreign companies.