Hollywood star George Clooney took up his new role as UN messenger of peace today.

The United Nations investigated more than 300 members of UN peacekeeping missions for alleged sexual exploitation and abuse during the past three years and more than half were fired or sent home, a senior UN official said.

Four peacekeepers from Bangladesh have been sent home and 13 other UN personnel serving in southern Sudan are under investigation for alleged serious misconduct, including sexual exploitation and abuse, the United Nations said tonight.

United Nations peacekeepers in southern Sudan reportedly face several allegations of raping and sexually abusing children, some as young as 12.