Kofi Annan, one of the world’s most celebrated diplomats and a charismatic symbol of the United Nations who rose through its ranks to become the first black African secretary-general, has died.

His foundation announced his death in a tweet, saying he died at the age of 80 after a short, unspecified illness.

His homeland of Ghana was shaken by his death. President Nana Akufo-Addo called for a week with flags at half-mast, and said: “One of our greatest compatriots. Rest in perfect peace, Kofi. You have earned it.”

He added in a tweet that Mr Annan’s wife Nane said he had “died peacefully in his sleep”.

Mr Annan spent virtually his entire career as an administrator in the UN.

He served two terms as secretary-general from January 1997 to December 2006, capped nearly midway when he and the UN were jointly awarded the Nobel Peace Prize in 2001.

During his tenure, he presided over some of the worst failures and scandals at the world body, one of its most turbulent periods since its founding in 1945.

Challenges from the outset forced him to spend much of his time struggling to restore its tarnished reputation.

His enduring moral prestige remained largely undented, however, both through charisma and by virtue of having negotiated with most of the powers in the world.

When he departed from the UN, he left behind a global organisation far more aggressively engaged in peacekeeping and fighting poverty, setting the framework for the UN’s 21st-century response to mass atrocities and its emphasis on human rights and development.

“Kofi Annan was a guiding force for good,” current secretary-general Antonio Guterres said.

“It is with profound sadness that I learned of his passing. In many ways, Kofi Annan was the United Nations. He rose through the ranks to lead the organisation into the new millennium with matchless dignity and determination.”

Kofi Annan with Nelson Mandela
Kofi Annan with Nelson Mandela in 2007 (AP)

Even out of office, Mr Annan never completely left the UN orbit. He returned in special roles, including as the UN-Arab League’s special envoy to Syria in 2012.

He remained a powerful advocate for global causes through his eponymous foundation.

German Chancellor Angela Merkel said Mr Annan “inspired me and many others with his ideas, his firm convictions and, not least, his charisma”, adding that he had shaped the United Nations “like hardly anyone before him”.

European Commission President Jean-Claude Juncker said he was mourning the “passing of my old friend and inspiration”.

“We are devastated,” the Nelson Mandela Foundation says in a statement. “Africa and the world has lost a special human being.”

Nigeria’s Amina Mohammed, the UN deputy secretary-general, says in a tweet that Mr Annan “gave hope to the voiceless” and she calls him “my friend, my hero, my inspiration”.

Russian President Vladimir Putin said he admired Mr Annan for his wisdom and courage.

“I sincerely admired his wisdom and courage as well as his ability to make balanced decisions even under the most dire and critical circumstances,” Mr Putin said, adding: “Russians will keep the memory of him forever.”

President Emmanuel Macron tweeted to say that “we will never forget his calm and resolute look, nor his strength in battles”.

Former South African archbishop Desmond Tutu said “we give great thanks to god” for him. He said MR Annan “represented our continent and the world with enormous graciousness, integrity and distinction”.

Mr Annan is survived by his wife and three children.