Former U.N. Secretary-General and Nobel Peace Prize laureate Kofi Annan died on Saturday at the age of 80, his foundation said, after decades of championing efforts to try to end protracted conflicts in Africa, Asia and the Middle East.

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 after a short undisclosed illness with “immense sadness”, saying he was surrounded in his last days by his second wife Nane and children Ama, Kojo and Nina.

After rising through the ranks of the United Nations, Annan served two terms as U.N. 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 the 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,” U.N. Secretary-General Antonio Guterres, whom Annan had chosen to head the U.N. refugee agency, said in a statement.