Afghan doctors delivered medicines Sunday for 21 South Koreans kidnapped by Taliban rebels in Afghanistan more than two weeks ago.

The head of a private Afghan clinic said his team had dropped more than US$1,200 worth of antibiotics, pain killers, vitamin tablets and heart pills in an area of desert in the Qarabagh district of Ghazni province as instructed by the rebels.

"This is a big achievement. Among the Koreans are doctors who know how to use these medicines," Mohammad Hashim Wahaj told reporters in Ghazni, the main town of the province, where 23 South Korean church volunteers were snatched from a bus on July 20.

The Taliban have killed two of their captives and are threatening to kill the rest if the Afghan government fails to release rebel prisoners. Kabul has refused to free jailed Taliban, saying that would just encourage more kidnappings.

The hostage issue is likely to cast a shadow over two days of security talks between Afghan President Hamid Karzai and US President George W. Bush at the US presidential retreat, Camp David, which began on Sunday.

Wahaj said he had been in contact with the kidnappers who told him two of the remaining hostages were seriously ill. The Taliban were willing to free those two hostages, he said, but only if two Taliban prisoners were also freed.

The insurgent demand for prisoners to be released has proved a sticking point in all negotiations so far.

A South Korean delegation was in Ghazni seeking face-to-face talks with the kidnappers to try to break the deadlock.

But the Taliban said on Sunday there was no agreement on where to hold direct talks with the Korean diplomats. The Taliban want negotiations in areas they control or with UN guarantees for their safety if held elsewhere.

Meanwhile, four Afghan workers of a private company were kidnapped by unidentified militants in the eastern Kunar province on Sunday, a provincial government spokesman told Xinhua.

Some militants rushed to a construction site and took away the four workers who were building a school in Watapur district, Shah Hussein Mangal said.

No one has claimed responsibility, and it was not immediately known what motivation was behind the kidnapping.

(China Daily via agencies, Xinhua News Agency, August 6, 2007)