Namibian President Hage Geingob has died at the age of 82, his office has said, less than three weeks after it was announced he would undergo treatment for cancer.

Geingob died on Sunday at Lady Pohamba Hospital in the capital Windhoek with his wife and his children at his side, acting president Nangolo Mbumba said in a statement posted on Geingob’s official Facebook page.

“The Namibian nation has lost a distinguished servant of the people, a liberation struggle icon, the chief architect of our constitution and the pillar of the Namibian house,” Mbumba said.

“At this moment of deepest sorrow, I appeal to the nation to remain calm and collected while the Government attends to all necessary state arrangements, preparations and other protocols. Further announcements in this regard will be made.”

Geingob’s office announced last month that he had begun treatment following the discovery of “cancerous cells” during a routine colonoscopy and gastroscopy.

The announcement did not provide details of the African leader’s diagnosis or prognosis but said he would continue to carry out his presidential duties.

Geingob’s office later announced that he would travel to the United States for medical care and would return to Namibia on February 2.

Geingob, who also served a 12-year stint as prime minister, had a history of health problems that preceded his election as Namibia’s third president in 2014.

In 2013, the anti-apartheid activist-turned-politician underwent brain surgery, and the following year he revealed that he had survived prostate cancer.