Candles are lit in front of the portrait of former UN Secretary General Kofi Annan during a memorial ceremony at Palais des Nations, in Geneva, Switzerland, Aug. 20, 2018. (Xinhua/Xu Jinquan)

UNITED NATIONS, Aug. 20 (Xinhua) -- The United Nations will hold events to pay tribute to former Secretary-General Kofi Annan, who died on Saturday at the age of 80.

The current UN secretary-general, Antonio Guterres, will lay a wreath in honor of Annan and deliver a speech at a ceremony on Wednesday morning at UN headquarters in New York, said Stephane Dujarric, spokesman for Guterres.

A book of condolences will be in place at UN headquarters till the end of the week, said Dujarric, who also served as Annan's spokesman.

The United Nations flag flies at half mast in memory of the late former UN Secretary-General Kofi Annan, at the UN headquarters in New York, on Aug. 18, 2018. (Xinhua/Li Muzi)

The UN flag has been at half-staff since Sunday and will continue through Tuesday.

The UN General Assembly will also hold an event in memory of Annan. The timing and format of such an event will be discussed on Monday afternoon, said Brenden Varma, spokesman for the president of the General Assembly.

Annan, a Ghanaian diplomat, served as UN secretary-general for 10 years till the end of 2006. In a statement on Saturday, Guterres described Annan as "a guiding force for good" and a good friend and mentor of his.