Kofi Annan, who died on Saturday at the age of 80, led the United Nations through the divisive years of the Iraq war and the trauma of the September 11, 2001 attacks.

The first secretary-general from sub-Saharan Africa, Ghanaian-born Annan was credited for raising the UN's profile during his two-term tenure, from January 1997 to December 2006.

The charismatic, quiet-spoken career diplomat will be remembered as the United Nations' star secretary-general - and arguably the world body's most popular leader.

But, as peacekeeping chief, two of the UN's darkest chapters - the Rwandan genocide and the Bosnian war - happened on his watch.

"I have sought to place human beings at the center of everything we do - from conflict prevention, to development, to human rights," Annan said in his 2001 speech after accepting the Nobel Peace Prize.

At the time, as the world was reeling from the September 11 attacks, Annan and the organization were jointly given the honor "for their work for a better organized and more peaceful world."