The head of the United Nations Population Fund, Babatunde Osotimehin, a champion for girls' and women's health, has died suddenly at his home, the UNFPA said on Monday.
"This is a devastating loss for UNFPA and for the people, especially women, girls and youth, he dedicated his life to serving, starting from when he became a doctor in Nigeria," the U.N. agency said in a statement. The cause of death was unclear.
"Dr. Osotimehin was bold and never afraid of a challenge and his strong leadership helped keep the health and rights of the world's women and girls high on the global agenda."
Osotimehin, a former Nigerian health minister, was particularly committed to ending preventable maternal deaths, tackling unmet demand for family planning and eliminating harmful practices against women and girls, UNFPA said.
U.N. Secretary-General Antonio Guterres tweeted: "I mourn the death of UNFPA chief Dr Babatunde Osotimehin. Our world lost a great champion of well-being for all, especially women & girls."
Others paying tribute on twitter included the head of UNAIDS, Michel Sidibe, and former New Zealand prime minister, Helen Clark.
The UNFPA said it was "dedicated to continuing Dr. Osotimehin's grand vision for women and young people."
Osotimehin, who was 68, had headed the UNFPA since 2011.
He was Nigerian minister of health from 2008 to 2010 and before that served as director-general of his country's National Agency for the Control of AIDS.
Osotimehin qualified as a doctor from the University of Ibadan, in 1972, and subsequently received a doctorate in medicine from the University of Birmingham, England.
He was married with five children and several grandchildren.