George Clooney has donated $5.6 million to the United Nations peacekeeping force in war-torn Sudan, to enable the team to buy a fleet of helicopters.

The kind-hearted actor, who is a U.N. Messenger of Peace, has become a leading celebrity advocate for action against genocide in the Sudan after filming a documentary about the ongoing violence and refugee crisis there last year.

He has also set up the Not On Our Watch organisation with his Ocean's Thirteen castmates Brad Pitt, Matt Damon and Don Cheadle - to help provide humanitarian aid in the region.

But when Clooney learned of the plight of the U.N. peacekeeping force Unamid in Darfur, he immediately dug deep in his pocket to do something about it.

A source explains, "George was horrified by the Sudanese government's 'scorched earth' (bomb) attacks on western Darfur last month.

"And when he was told that Unamid officials felt they could have done something about the attacks if they'd had the right equipment - they need 18 helicopters and so far have none - he decided to put his money where his mouth is."