Taliban militants who have been holding 19 South Koreans for more than a month renewed a threat yesterday to kill them if their demands are not met.
A purported rebel spokesman, Zabihullah Mujahed, said some of the captives were sick and they were also suffering from lack of proper food.
"If the demands of the Taliban are not met the Korean hostages face death," Mujahed said in a telephone call from an unknown location. "Although we want this crisis to be solved through negotiations, it seems the US authorities are creating problems."
He did not, however, set any deadline and it was impossible to verify his comments independently.
The South Korean aid workers were seized while travelling in southern Afghanistan on July 19, a day after a German engineer was kidnapped nearby.
The Islamic militant group has demanded the release of some of its jailed fighters in exchange for the hostages -- a demand the government in Kabul has so far rejected.
Mujahed said weather conditions and lack of "proper food" in Ghazni Province, which lies to the southwest of Kabul, meant life for the hostages was increasingly harsh.
Meanwhile, the governor of the southeastern province of Khost survived an assassination attempt yesterday when a suicide bomber struck his convoy, witnesses and officials said.
At least three of governor Arsala Jamal's bodyguards were killed in the attack, which occurred close just outside Khost town, they said.
Khost lies near the border with Pakistan and has suffered a spate of attacks in recent months.
Also yesterday, Taliban and Afghan forces clashed in two separate districts of Ghazni Province, the two sides said.