Bono given award for African work

The star was presented with the accolade in the US city of Philadelphia by last year's winner, George Bush, the father of the current US president.

He will donate the $100,000 (£49,200) cash prize to the Debt Aids Trade Africa charity he founded in 2002.

Speaking at the ceremony, the musician said: "When you are trapped by poverty, you are not free."

He added: "When trade laws prevent you from selling the food you grew, you are not free.

"When you are a monk in Burma this very week, barred from entering a temple because of your gospel of peace... well, then none of us are truly free."

Bono also called on Americans to continue helping the world.

"America has so many great answers to offer," he said. "We can't fix all the world's problems, but the ones we can, we must."

The Liberty Medal, established in 1988, is awarded by the US National Constitution Center to those who have "demonstrated leadership and vision in the pursuit of liberty".

The organisation describes itself as being dedicated to increasing public understanding of, and appreciation for, the US constitution, its history and its contemporary relevance.