NO DEAL
The Islamic movement killed two male hostages after previous deadlines expired.
Afghan officials have said no deal would be struck with the Taliban and demanded the unconditional release of the remaining captives, 18 of them women. The group of 23 had been sent by a Christian church in Seoul to do relief work in Afghanistan.
President Hamid Karzai came under sharp criticism after releasing a group of Taliban prisoners in March in return for the freedom of an Italian journalist.
South Korea is under intense pressure to bring the hostages home but concedes it has few cards to play. Seoul has called for "flexibility", a comment analysts say is directed at the United States to pressure Kabul to strike a deal with the kidnappers.
A U.S. State Department spokesman has said Washington "does not make concessions to terrorists".
The abduction of the Koreans comes after 18 months of rising violence in Afghanistan, the bloodiest period since the Taliban were ousted from power by U.S.-led and Afghan forces in 2001.
A day before seizing the Koreans, the Taliban abducted two German aid workers and five Afghan colleagues in Wardak province, which, like Ghazni, lies to the southwest of Kabul.
One German was found shot dead and one of the Afghans managed to escape. The other German and four Afghans were still being held.
The Taliban have demanded Germany pulls its 3,000 troops out of Afghanistan as the main condition for freeing the other German.
Al Jazeera aired silent footage of a man against a rocky backdrop, guarded by a militant with a rocket-propelled grenade.
"The German hostage Rudolf B. ... urged Germany and the United States to pull out their forces from Afghanistan and urged his country to help save his life and secure his return to his homeland and family," the station presenter said.
German Chancellor Angela Merkel has said Berlin would not give in to the kidnappers' demands.
Separately, the Taliban have killed four Afghan judges they kidnapped in Ghazni two weeks ago, a provincial official said on Wednesday. The bodies of the four, killed on Tuesday night, were found to the south of the town of Ghazni on Wednesday, he added.
