Afghanistan: August 4, 2007. (AFP) - A purported hostage made an emotional plea for help in a telephone call with AFP on Saturday, as an Afghan negotiator ruled out an exchange of Taliban prisoners for 21 South Koreans. "They threaten us, they tell us they will kill us," a woman who was said by the Taliban to be one of its hostages said in a discussion set up by the militants main spokesman, Yousuf Ahmadi. "It is difficult, they are very dangerous," she said, speaking at times in English and at times in Dari. She gave her name as what sounded like Sing Jo-Hin but there was no way of verifying she was one of the hostages. "Most of us are sick now," she wept. "Our condition is worsening every passing day. We cannot eat anything and we cannot sleep too. And we miss Korea and our homes." She pleaded with the South Korean and Afghan governments, UN chief Ban Ki-moon and Pope Benedict XVI to help win the release of the aid mission. The Taliban kidnapped 23 South Koreans on July 19 and have murdered two of them. They have threatened to execute more unless at least eight of their men are released from jail. The militants said after their latest deadline expired Wednesday they had not killed any more hostages because they were hoping for results from talks with the South Koreans. "They told us that they are in negotiations with the Afghan and American governments to convince them to free Taliban prisoners in exchange for the South Korean hostages," Ahmadi said Friday. He said a Taliban delegation was ready to meet South Korean representatives face-to-face -- in another country if necessary as long as the United Nations guaranteed the "safe return" of the negotiators. But an Afghan negotiator again ruled out Saturday an exchange of Taliban prisoners to free the 21 South Koreans. Negotiations over the church aid workers were now being conducted mainly by a South Korean delegation, said Mahmood Gailani, a member of the negotiating team who last week described the Afghan side`s talks with Taliban as "stuck". "They can only talk about money, ransom," he told AFP, referring to the South Koreans. "Not only the Americans are opposed to an exchange of prisoners, it`s against the policy of the government." The United States was the leading critic of a prisoner exchange in March that freed an Italian hostage but put top Taliban back in the fight against the government and its international allies, who have about 50,000 soldiers here. President Hamid Karzai vowed then such a deal would never be repeated with critics saying it could encourage kidnappings. A 62-year-old German engineer who was captured a day before the South Koreans, is being still held, along with four Afghans, by militants who are believed to be closely linked to the Taliban. He was seized with another German who collapsed days later and was then shot dead. The families of the South Korean hostages visited a mosque in Seoul Saturday and appealed for Muslims to help free them. "These children went to act on their love beyond race, religion and borders," they said in a letter handed to the mosque. The second hostage to be shot by the Taliban, 29-year-old Shim Sung-Min, was buried on Saturday. The pastor who had headed the mission was shot dead days before him. The Taliban, linked to Al-Qaeda, have also tried to use the kidnapping of foreign nationals to pressure the more than 30 countries with troops in Afghanistan to pull out. The tactic is part of a broad strategy against Karzai`s government, which replaced the Taliban administration driven from power in 2001 by a US-led coalition. The rebel insurgency sees almost daily bloodshed. In a new attack, a suicide car bomb exploded near international troops in the south Saturday, killing two Afghan civilians, police said