The Taliban has set a new deadline for the Afghan government to meet its demands in order to save 21 South Koreans it is holding hostage.
The kidnappers have set of noon Afghanistan time on Wednesday as the new deadline.
The hardline Islamic militia wants the government to free at least eight Taliban prisoners in Afghan jails, a demand negotiators have rejected.
The Taliban have said that if its demands are not met by Wednesday's deadline it will start killing the rest of the South Koreans.
The 23 South Koreans were kidnapped while on an Christian aid mission on 19 July.
The latest demand comes after a second hostage was killed.
Shim Sung-Min's body was found with bullet wounds in an area of the southern province of Ghazni, about 140km south of Kabul today.
Mr Shim, a former IT employee who resigned to do volunteer work for the Seoul-based church that sent the Christian mission to Afghanistan, was the second hostage to be murdered by the militants.
Last week the leader of the group, 42-year-old Bae Hyung-Kyu, was shot dead.
Negotiations had reached a deadlock with Afghan authorities demanding the release of the hostages before any demands were met. A Taliban spokesman said Mr Shim was killed because Afghan authorities were ignoring their demands.
South Korea has said it will hold the kidnappers responsible for the taking of innocent lives.
The village in Ghazni where the body was found is some 80km from where the group of 18 women and five men were seized, undermining statements by Afghan officials who said government forces had the kidnappers surrounded.
The hostage crisis has focused attention on growing lawlessness in Afghanistan, where Taliban influence and attacks are spreading to areas previously considered safe.
