Afghanistan's Foreign Ministry said Saturday that one German hostage was still alive and a second had died of a heart attack, despite a claim by a purported Taliban spokesman that both had been fatally shot.

"The information that we and our security forces have is that one of these two who were kidnapped died of a heart attack," said Foreign Ministry spokesman Sultan Ahmad Baheen. "The second hostage is alive and we hope that he will be released soon and we are trying our best to get him released."

A man claiming to speak for the Taliban said the group shot and killed the two German engineers after a deadline passed for the German and Afghan governments to meet its demands.

The purported spokesman, Qari Yousuf Ahmadi, announced the executions on Saturday but gave no proof. He said the Taliban would give information about the bodies later.

Ahmadi also said the militants were willing to release 23 South Korean hostages in exchange for imprisoned Taliban fighters. He said the Afghan and South Korean governments had until Sunday evening to agree to the
exchange of 23 Taliban militants or the Korean hostages would be killed.

The German newspaper Bild am Sonntag, quoting unidentified German government sources, reported on Saturday that the man who announced the killings does not speak for the kidnappers.

The Taliban wants Germany to withdraw 3,000 soldiers who are stationed in the mostly peaceful northern part of Afghanistan.

The two Germans were abducted on Wednesday, along with five Afghan colleagues, in the southern province of Wardak while working on a dam project.

On Thursday, militants kidnapped the South Koreans, who were travelling on a bus in Ghazni, one province south of Wardak.

Ahmadi said previously the Korean missionaries would also be killed Saturday if South Korea didn't withdraw the 200 troops it has in Afghanistan, but he gave no information about their condition. South Korea's soldiers are largely assigned to humanitarian projects such as medical assistance and reconstruction work.

The South Korean government informed parliament late last year that it would terminate its troop mission in Afghanistan and bring them home before the end of this year.

With files from the Associated Press