GHAZNI, Afghanistan (AFP) - Afghanistan's Taliban set the government a new deadline of noon (0730 GMT) Wednesday to meet its demands in order to save 21 South Koreans, a day after a second hostage was killed and as a German one reportedly pleaded for his life.
The hardline Islamic militia wants the government to free at least eight Taliban prisoners in Afghan jails, a demand negotiators have rejected.
"If our demands are not met by then, we will start killing the rest of the South Koreans," Taliban spokesman Yousuf Ahmadi told AFP.
The bloodied corpse of the second person to be killed since 23 were kidnapped nearly two weeks ago was found early Wednesday in the southern province of Ghazni, about 140 kilometres (90 miles) south of Kabul.
The body was dumped in a field just off a main road, with his hands tied and bullet wounds to the head.
South Korea's foreign ministry identified the victim as Shim Sung-Min, 29, as the country reacted with outrage.
"The Korean government strongly condemns and urges an immediate end to these heinous acts of killing innocent people in order to press for demands that it can't meet," the presidential office in Seoul said.
UN chief Ban Ki-moon also deplored the killing and voiced deep concern about the safety of other captives held by the Taliban.
"These hostages include many young women who came to help the people of Afghanistan and they should not be made part of the conflict in that country," he was cited as saying by his press office.
South Korean media reports said Shim had quit his job at a Seoul IT company two months ago to become a teacher to the disabled at a Seoul church which had then sent him to Afghanistan on an aid mission.
The body of pastor Bae Hyung-Kyu, 42, who had been leading the group on the mission to the risky south, was found in the same area last Wednesday.
In Cairo, the Arab League and Al-Azhar, the premier Sunni institution of learning, also condemned the killings and called for the immediate freeing of the remaining hostages, 16 of them women.
A Taliban spokesman said yesterday two female hostages were gravely ill.
"Their condition is very bad. We don't have enough medicines -- maybe they will die," Yousuf Ahmadi said, pressing negotiators to agree to his organisation's demands so the women could be released.
The South Korean government meanwhile called for "flexibility" to save the 21 captives.