The U.S. government was not aware of talks to release a South African hostage in Yemen who was killed during a botched special forces raid, the U.S. ambassador to South Africa claimed Monday.

Pierre Korkie, a 57-year-old South African teacher who was taken hostage by al-Qaida militants in Yemen more than a year ago, was killed on Saturday, hours before he was due to be released.

South African relief organization Gift of the Givers said they had negotiated for Korkie to be freed and had notified his widow Yolande that he would be home soon.

But ambassador Patrick Gaspard told a radio station the U.S. was "completely unaware" of Korkie's imminent release.

"The U.S. government was absolutely unaware of negotiations between Gift of the Givers and these brutal al-Qaida hostage takers," Gaspard told talk radio station 702.

He said the U.S. was also unaware Korkie was being held in the same location as Luke Somers, an American photojournalist who was also killed in Saturday's failed raid by U.S. forces in Yemen's southeastern Shabwa province.

"The president learned through the National Security Council that the American hostage Luke Somers faced an imminent threat," said Gaspard.

"There was a video released that he would be executed within 72 hours. Upon that information . . . President Obama authorized a rescue mission to to attempt to free Mr Somers so that he would not face the same fate that we've seen others endure recently."