(Adds six NATO-led troops killed, paragraphs 10-11)

By Sayed Salahuddin

KABUL, July 23 (Reuters) - The Taliban on Monday gave 23 Korean hostages another 24 hours to live to allow the South Korean government to open direct talks with the kidnappers, a Taliban spokesman said on Monday.

Spokesman Qari Mohammad Yousuf said negotiations with the Afghan government were going nowhere and South Korea had until 1430 GMT on Tuesday to agree to withdraw its 200 troops from Afghanistan. Unless it did so, the Taliban would start killing the captives.

It was the second time the Taliban had extended their deadline by 24 hours.

Yousuf said a German hostage the Taliban had said they had killed was still alive along with four Afghans and they were still held hostage.

The same spokesman had previously said two German engineers and five Afghans seized by the Taliban had been killed. He said the group holding them had told him they were about to kill the hostages as government troops were closing in on them and then he had lost touch with the militants as they made their escape.

Neither Germany nor South Korea has shown any sign they might give in to Taliban demands and pull their troops out, nor has Kabul indicated it would release Taliban prisoners as also demanded by the Islamist guerrillas.

"We will not give in to blackmail," said German Chancellor Angela Merkel.

But the kidnappings risk weakening public support for military involvement among the 37 nations contributing to peacekeeping forces in Afghanistan.

While NATO and U.S. forces say their troops, alongside the Afghan army, routinely rout Taliban guerrillas in combat, the insurgents are increasingly resorting to suicide bombs and kidnapping.

Six NATO-led soldiers were killed in the past two days in the increasing violence. Four soldiers were killed and one wounded when their convoy was struck by an explosive device in eastern Afghanistan, the U.S. military said.

One Norwegian soldier was killed in a clash to the south of Kabul on Monday and another NATO solider was killed in an ambush in the eastern province of Kunar, the alliance said.

NEGOTIATIONS

The 23 Korean Christians from the "Saemmul Church" in Bundang, a city outside South Korea's capital, Seoul, were in good health, the Taliban spokesman and government negotiator said.

While tribal elders tried to mediate between the militants and government negotiators, Afghan forces have surrounded the group of some 70 kidnappers in the Qarabagh area of Ghazni.

"Contacts with militants are being made through several channels," South Korea's Yonhap News quoted an unnamed government official as saying.

Most of the Koreans are in their 20s and 30s, and include nurses and English teachers.

A delegation of Korean diplomats were aiding the negotiations, a South Korean embassy official said.

"The diplomats from the embassy are still in negotiations with community elders of Ghazni province to solve the matter peacefully and secure the safe release of the hostages," he said.

South Korea ruled out a rescue bid without its say-so.

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