(Adds Taliban comments)

By Yousuf Azimy

GHAZNI, Afghanistan, Aug 1 (Reuters) - The remaining South Korean hostages held in Afghanistan are still alive, the Taliban said on Wednesday, while the army warned villagers to evacuate areas near where the insurgents are thought to be holding them.

Taliban spokesman Qari Mohammad Yousuf said all 21 hostages were alive despite the expiry of a deadline after which he had warned the kidnappers would start killing the captives unless the Afghan government freed jailed insurgents.

"Yes, they are alive," Yousuf told Reuters by telephone from an unknown location. "But the danger (of killing) them remains. It is possible that they will be killed," he said, without giving a time frame.

The Afghan government has refused to give in to demands to free Taliban prisoners, saying that would only encourage further abductions.

Twenty-three South Korean church volunteers were snatched from a bus on the main road south from the capital Kabul as it travelled through Ghazni province last month.

Two male Koreans have since been killed by the kidnappers after their demands were ignored.

The Defence Ministry said army helicopters had dropped leaflets in several districts of Ghazni province warning residents to move to secure areas to avoid civilian casualties during an operation to be launched in the "coming weeks".

But the ministry said it was a routine operation not linked with the kidnapping. Both Afghan and foreign troops were stationed in the area, a local official said.

RELATIVES DESPERATE

Any rescue operation would be fraught with danger as the Taliban have split the hostages into small groups and are holding them in several locations in the mainly flat but lush region.

The Taliban spokesman again warned that any rescue bid would jeopardise the lives of the South Koreans, 18 of them women. He said Taliban fighters had not detected any rescue operation, but had seen increased troop movements in the area.

"No military operation has yet begun," said Yousuf. "But our mujahideen have been noticing provocations since yesterday."

Afghan President Hamid Karzai was criticised in March after releasing a group of Taliban prisoners in return for the freedom of an Italian journalist. He later said he would not make any hostage deals with the Taliban again.

The hostages' desperate relatives, keeping an agonising vigil in Seoul, appealed to the U.S. government to intervene. South Korean lawmakers also made a joint appeal to Washington to act.

The group was sent by a Christian church in Seoul to do relief work in Afghanistan.

"SERIOUSLY ILL" HOSTAGES

The Taliban spokesman said two women hostages were now seriously ill.

"The majority of the hostages are ill, but two females are seriously ill and there is this possibility that they may die," Yousuf said.

He added the pair were suffering from an unknown illness and the Taliban did not have the right medicines to treat them.

The abduction of the Koreans comes after 18 months of rising violence in Afghanistan, the bloodiest period since the Taliban was ousted from power by U.S.-led and Afghan forces in 2001.

A day before seizing the Koreans, the Taliban abducted two German engineers and five Afghan colleagues in Wardak province, which, like Ghazni, lies to the southwest of Kabul.

One German was found shot dead and one of the Afghans managed to escape. The other German and four Afghans are still being held. The Taliban have demanded Germany pulls its 3,000 troops out of Afghanistan as the main condition for freeing the other German. (Additional reporting by Sayed Salahuddin and Hamid Shalizi in Kabul and Seoul bureau)

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