Nobel Peace Prize winner and former UN Secretary General Kofi Annan has died aged 80.
The United Nations Migration Agency confirmed his death writing online: "It is with immense sadness that the Annan family and the Kofi Annan Foundation announce that Kofi Annan, former Secretary General of the United Nations and Nobel Peace Laureate, passed away peacefully on Saturday 18th August after a short illness"
Mr Annan served with the UN from 1997 to 2006. He later served as the UN special envoy for Syria
He was awarded the Nobel Peace prize in 2001 jointly with the United Nations organisation for his efforts to 'revitalise' the UN and for 'having given priority to human rights'.
Mr Annan, of Ghanaian nationality, died in hospital in Bern, Switzerland, in the early hours of Saturday, two close associates told the Reuters news agency.
Theresa May said in a tweet says Annan "made a huge contribution to making the world he has left a better place than the one he was born into."
President Emmanuel Macron wrote online that "we will never forget his calm and resolute look, nor his strength in battles."
NATO Secretary-General Jens Stoltenberg said on Twitter that Annan's "warmth should never be mistaken for weakness. ... The U.N. and the world have lost one of their giants."
Current secretary-general Antonio Guterres said: "Kofi Annan was a guiding force for good.
"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."
During his time as secretary general, he clashed with Tony Blair over the 2003 invasion of Iraq by US and British forces, which he denounced as illegal.
However the former prime minister - whose time in No 10 coincided closely with Mr Annan's time in office - said their differences had not prevented them remaining good friends.
"I'm shocked and distressed to hear the news about Kofi. He was a good friend whom I saw only weeks ago," Mr Blair said in a statement.
"Kofi Annan was a great diplomat, a true statesman and a wonderful colleague who was widely respected and will be greatly missed."
Former prime minister Gordon Brown, who is currently the UN special envoy for global education, said Mr Annan had fought throughout his life against poverty and injustice.
"Kofi Annan was a leader of leaders, a wonderful humanitarian and the most compassionate and caring of individuals.
"Personally modest and always softly spoken, he was a titan amongst world statesman who saw wrong and righted it and who witnessed evil and always fought it.
"Even in his later years he fought against poverty, injustice and war with all the vigour of youth and I had the privilege of working with him in recent times."