“Extremely saddened by passing of Kofi Annan, a towering global leader and an unwavering champion for peace, justice and rule of law. Rest in peace my dear old friend,” Zarif said on his Twitter account on Saturday.
Annan died after a short illness at the age of 80, his foundation announced in a statement.
"It is with immense sadness that the Annan family and the Kofi Annan Foundation announce that Kofi Annan… passed away peacefully on Saturday 18th August after a short illness," the foundation said.
Annan, of Ghanaian nationality, died in a hospital in Bern, Switzerland, in the early hours of Saturday.
In 2001, Anan won the Nobel Peace Prize for humanitarian work and for having revitalized the UN.