JOHANNESBURG (AFP) - A South African teacher being held hostage in Yemen and whose kidnappers had threatened to kill him is still alive but in poor health, an organisation working to free him said on Saturday.

English teacher Pierre Korkie, 56, was abducted along with his wife last May in the Yemeni city of Taiz by members of Al-Qaeda in the Arabian Peninsula, who asked for a ransom of US$3 million (S$3.8 million) and had threatened to kill him if not paid by Friday.

"They said he's still alive, and we will stop the execution," said Imtiaz Sooliman, president of the Gift of the Givers charity.

"Then, on their own, they said, but Pierre is not in very good health." Sooliman said the kidnappers had agreed to extend their deadline by three weeks.

Korkie's wife Yolande was released on January 10 and has since returned to South Africa to fight for his release. The couple had lived and worked in Yemen for four years.

The South African government sent its deputy foreign minister to Yemen on Friday to try to secure Korkie's release.

Hundreds of people have been abducted in Yemen in the past 15 years, nearly all of whom have been freed unharmed. The hostages are used as bargaining chips in disputes with the central government.