Afghan army choppers dropped leaflets warning the Taliban of an assault to rescue 21 South Korean hostages, whose captors said were still alive after another deadline expired.

There was no confirmation that a military operation had begun in Ghazni province, where the Christian volunteers were abducted nearly two weeks ago by the Taliban.

The Islamist insurgents, who are demanding the release of rebel prisoners, killed two men from the original group of 23 after previous deadlines they had set expired.

"The hostages are alive," Khowja Seddiqi, district chief of Qarabagh, told Reuters. "The national army has dropped leaflets from helicopters telling people in several districts to evacuate their houses because it wants to launch an operation."

Afghan army and foreign troops were stationed in the area, but no operation to rescue the hostages had begun, Seddiqi said.

A Taliban spokesman also said the hostages were alive, but two women were seriously ill. He said the pair suffered from an unknown illness and the Taliban did not have the right medicines to treat them.?

Earlier the Defence Ministry said the Afghan National Army had launched an operation in Ghazni, but insisted it was "routine" and was not linked with the kidnapping.

The BBC, quoting local officials, said fighting had erupted in the area where the hostages were being held.

Earlier in the day, a Taliban spokesman said the group was expecting to hear from Afghan mediators over its demand for the government to free rebels from jail, but insisted some of the hostages would be killed if that demand was not met by 07:30 GMT (3:30 PM, Beijing time).

The head of the Afghan government team tasked with trying to secure the release of the hostages has not ruled out use of force to end their ordeal.

A South Korean Foreign Ministry official said: "We have sent a message to the Afghanistan government that a rescue operation should not take place without the South Korean government's consent."

Also on Wednesday, German officials reaffirmed Berlin would not give in to pressure from the Taliban to withdraw troops from Afghanistan, after Al-Jazeera television broadcast a video showing a German hostage.

The man appeared on Al-Jazeera on Tuesday in a video without sound but a presenter said the hostage, which the broadcaster identified as Rudolf B., urged Germany and the United States to pull their troops out of Afghanistan to help save his life.

"We cannot bow down to such demands," said Peter Struck, the parliamentary leader of the center-right Social Democrats, who share power with Chancellor Angela Merkel's conservatives.

Struck, a former defense minister, said there was no question of withdrawing the 3,000 troops Germany has in the north of Afghanistan.

A Foreign Ministry spokeswoman said experts were analyzing the video, which showed one of the militants pointing a racket-propelled grenade launcher at the man.

"This is a targeted attempt at intimidation," Julia Gross told a news conference, adding: "The government is working around the clock to try to establish contact with the hostage and try to free him."

The Taliban seized two Germans and five Afghans in the Wardak province earlier this month. The body of one of the Germans was found with bullet wounds, but the other German and four Afghans were still being held by the Taliban.

One of the Afghan captives managed to escape.

The insurgents have demanded the release of 10 Taliban prisoners held by the Afghan government and the withdrawal of German troops from Afghanistan in exchange for the hostages' freedom.

Merkel has previously said Berlin would not give in to the kidnappers' demands.

Germany is struggling to cope with a new threat from hostage-takers in Afghanistan and Iraq.

This has forced the government to take a new look at how it deals with kidnappers, with some hard-liners insisting that all consideration of ransom payments must stop.

Berlin's official line, repeated on numerous occasions in recent weeks, is that it will not bow to militant demands.

"We undertake everything in our power, pursue every responsible avenue to protect the lives of German citizens," government spokesman Thomas Steg said this week. "Our stance is unchanged. The German government cannot be blackmailed."

But it is an open secret that Germany has paid in the past.

(China Daily via agencies August 2, 2007)