Security officials say assailants in an eastern Libyan city have thrown a homemade bomb at a U.N. convoy in which the world body's top diplomat in the country was traveling.

They said that neither Ian Martin nor any of his traveling companions were harmed in the Tuesday afternoon attack in Benghazi and that authorities launched a search for the attackers.

A U.N. official confirmed that the attack had taken place. Like the security officials, he spoke on condition of anonymity because he was not authorized to speak to the media.

Libya has been hit by lawlessness since the ouster last year of Muammar Qaddafi, with militiamen who fought the dictator's forces refusing to stand down or hand over their weapons.