President Barack Obama criticised Zimbabwean leader Robert Mugabe and warned Africa not to repeat the mistakes that betrayed the hopes of an "independence generation," which included his own father.

"I'll be honest with you. I am heartbroken when I see what has happened in Zimbabwe," he said at the White House event to talk about the continent's future.

Obama invited 115 young Africans, selected as the region's future leaders, to take part in a three-day meeting  marking the 50th anniversary of independence in many of their countries, while looking toward the next 50 years.

As America's first black president whose father was Kenyan, Obama's words carry special weight in Africa. He urged greater press freedom, said corruption undermined support for foreign aid, and aimed harsh criticism at Zimbabwe's long-serving president.

"I think Mugabe is an example of a leader who came in as a liberation fighter and, I'm just going to be very blunt, I do not see him serving his people well," Obama told the meeting in response to a question about sanctions.

Next generation
Obama said he had deliberately reached beyond the current generation of African leaders to talk to young people who will shape the region's future and urged they understand corruption was the continent's enemy.

"If at a time of great constraint, we are coming up with aid, those aid dollars need to go to countries using them effectively," he said.

In a lighter moment, Obama recalled South Africa's successful staging of the soccer World Cup as a positive example of moving past white minority rule to democracy.

He spoke of "huge opportunities" Africa had missed and urged the audience to get it right this time.

"When my father traveled to the United States and got his degree in the early Sixties, the GDP of Kenya was actually on par, maybe actually higher, than the GDP of South Korea ... Now it is not even close. That is fifty years that was lost in terms of opportunities," Obama said.