Kofi Annan, the former UN secretary-general who won the Nobel Peace Prize for humanitarian work, has died aged 80, international diplomats say.

The UN's International Organization of Migration announced on its Twitter page.

Annan was the first black African to take up the role of the world's top diplomat, serving two terms from 1997 to 2006.

He later served as the UN special envoy for Syria, leading efforts to find a peaceful solution to the conflict.

Annan's tenure coincided with the Iraq War and the HIV/Aids pandemic.

Annan, served as the seventh UN chief for almost 10 years and was awarded the Nobel Peace Prize in 2001, died on Saturday.

"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," read a post on his Twitter account.