ADDIS ABABA: Barack Obama on Tuesday condemned African leaders who refuse to give up power and urged the continent to end "the cancer of corruption", in the first ever address to the African Union by a US president.

Obama said the rest of the world also needed to change its approach to Africa by boosting fair trade and not just providing aid handouts, and vowed that the United States stood with the region to defeat terrorism and end conflict.

The speech marked the end of a short tour that has seen Obama visit Kenya, his father's birthplace, and Ethiopia, from where he flew out on Air Force One after the speech.

Both are key security allies in the fight against Somalia's Al Qaeda-affiliated Shebab militants, but they were also challenged on concerns over democracy, human rights and graft.

"Africa's democratic progress is also at risk when leaders refuse to step aside when their terms end," Obama said, drawing huge applause and cheers from some sections of the audience in the AU's Nelson Mandela hall.

"No one should be president for life," he said, explaining that he was personally relishing handing over office in 18 months.

"I love my work, but under our constitution, I cannot run again. I actually think I'm a pretty good president, I think if I ran again I could win, but I can't," he said.

"And, I'll be honest with you, I'm looking forward to life after being president. I won't have such a big security detail all the time, it means I can take a walk, it means I can spend time with my family.

“The point is I don't understand why people want to stay so long.

"Especially when they've got a lot of money,” he said, drawing another huge cheer from the hall packed with diplomats but also many civil society activists.

'Cancer of Corruption'

Obama's keynote speech also went further on endemic and institutionalised graft, something he had pressed on in Kenya over the weekend as well.

"Nothing will unlock Africa's economic potential more than ending the cancer of corruption," Obama said, before speaking at length of the need for growth to be boosted by ending discrimination and sexual violence against women and girls.

Obama singled out Burundi's President Pierre Nkurunziza ─ whose successful bid for a third term provoked weeks of unrest in the small central African nation ─ as an example of the dangers of trying to stay put and risking "instability and strife".

At the same time, Obama said the world needed to "recognise Africa's extraordinary progress", and outlined how American businesses were increasing US trade with the continent.

Playing up his position as the first-ever African-American US president, he also cast Washington as a trusted partner of the continent, and took a veiled swipe at resource-hungry China ─ which has massively stepped up its presence in Africa, symbolised by the Chinese-built AU headquarters where he gave the speech.

"Economic relationships cannot simply be about other countries building infrastructure with foreign labour, or extracting Africa's natural resources," Obama said.

"Real economic partnerships have to be a good deal for Africa. They have to create jobs and capacity for Africans. That's the kind of partnership America offers."

Obama said the United States was also a solid security partner that would stand by Africa in dealing with terrorism and end conflict. He said continent's progress will "depend on security and peace".

"As Africa stands against terror and conflict, I want you to know the United States stands with you," he said, highlighting threats ranging from Somalia's Shebab, Boko Haram in Nigeria, insurgents in Mali and Tunisia, and Lord's Resistance Army rebels in central Africa.

Progress being made

Obama said the United States was backing AU military efforts and saluted the "brave African peacekeepers" battling militants.

"Many of these groups claim the banner of religion, but hundreds of millions of African Muslims know that Islam means peace. We must call groups like Al Qaeda, Daesh or the ISIL (self-styled Islamic State), Al Shebab and Boko Haram, we must call them what they are ─ murderers." He said progress against them was being made.

"Because of the AU force in Somalia, Al Shebab controls less territory, and the Somali government is growing stronger. In central Africa, the AU-led mission continues to degrade the Lord's Resistance Army," he said.

"In the Lake Chad basin, forces from several nations ─ with the backing of the AU ─ are fighting to end Boko Haram's senseless brutality." Many audience members emerged impressed ─ even if several African leaders may be less happy.

"It was excellent, inspiring," said Aeneas Chuma, a UN worker from Zimbabwe who said he was speaking in his personal capacity.

"He touched on all challenges for Africa, like the importance of good governance, the fact that this trend of leaders staying in power cannot continue." Addis Ababa university student Anatoli Bulti said Obama's address was "empowering".

"He spoke about a lot of issues that don't usually get addressed in this country: democracy, freedom. Coming from him it gives these issues a lot more weight." Following Obama's departure from Kenya, the country's police chief admitted that the US president's visit was a security "nightmare", but said the incident-free trip to Nairobi had proved a major confidence boost for security forces.

Read more: Africa must tackle ‘scourge’ of terrorism, leaders warn