Accra/Geneva: Former United Nations secretary general and Nobel Peace Prize laureate Kofi Annan died on Saturday at the age of 80, his foundation said.
Annan, a Ghanaian national, died in hospital in Bern, Switzerland, in the early hours, his close associates said.
In Geneva, the Kofi Annan Foundation announced his peaceful death with "immense sadness" after a short undisclosed illness, saying he was surrounded in his last days by his second wife Nane and children Ama, Kojo and Nina.
Annan served two terms as UN Secretary General in New York from 1997-2006 and retired to live in a Swiss village in the Geneva countryside. His 10-year-old foundation promotes good governance and transformation of African agriculture.
"In many ways, Kofi Annan was the United Nations. He rose through the ranks to lead the organization into the new millennium with matchless dignity and determination," UN Secretary General Antonio Guterres, whom Annan had chosen to head the UN refugee agency, said in a statement.
As head of UN peacekeeping operations, Annan was criticised for the world body's failure to halt the genocide in Rwanda in the 1990s.
As UN boss he was linked to peace efforts to reunite the divided island of Cyprus, submitting a reunification blueprint which was rejected in a referendum by Greek Cypriots in 2004.
He staunchly opposed the US-led invasion of Iraq in 2003 and later served as the first UN envoy at the start of Syria's war, but quit after world powers failed to fulfil their commitments, saying: "I lost my troops on the way to Damascus".
"The UN can be improved, it is not perfect but if it didn't exist you would have to create it," he told the BBC's Hard Talk during an interview for his 80th birthday last April, recorded at the Geneva Graduate Institute where he had studied.
"I am a stubborn optimist, I was born an optimist and will remain an optimist," Annan added.
Raila Odinga, Kenyan opposition leader and former prime minister, said on privately-owned Citizen TV: "We didn't expect Kofi to pass that abruptly. Kofi Annan is a man of integrity; a great African, a great leader of the world."
The Elders, a group of former leaders including Gro Harlem Brundtland and Mary Robinson, paid tribute to their inspiring chairman, noting his visits to South Africa and Zimbabwe in July.
UN high commissioner for human rights, Zeid Ra'ad al-Hussein, paid tribute to Annan as "humanity’s best example, the epitome, of human decency and grace".
Zeid, who has criticised major powers and other countries during his four-year term that ends later this month, said that whenever he felt "isolated and alone politically", he would go for long walks with Annan in Geneva.
"When I told him once how everyone was grumbling about me, he looked at me — like a father would look at a son — and said sternly: "You’re doing the right thing, let them grumble."Then he grinned!"