U.S. President Barack Obama has ordered flags to be lowered to half-staff until Monday' sunset to mourn the death of Nelson Mandela, who died at 95 on Thursday, according to a proclamation issued by the White House.

Flags shall be flown at half-staff at the White House and upon all public and military places nationwide until sunset, December 9, 2013 as "a mark of respect for the memory of Nelson Mandela", Obama ordered in the proclamation.

"Nelson Mandela is no longer with us, he belongs to the ages," he said.

South African President Jacob Zuma announced Mandela's death in a televised speech on Thursday.

"Madiba's 'long walk to freedom' gave new meaning to courage, character, forgiveness, and human dignity," U.S. Secretary of State John said in a statement, using Mandela's clan name and referring to his autobiography.

"There are some truly brave people in this world whom you meet and you're forever changed for the experience," Kerry said.

"President Nelson Mandela is gone, but his legacy and example will forever endure," U.S. National Security Advisor Susan Rice said in a statement.