The Tawhid and Jihad group of Jordanian militant Abu Musab al-Zarqawi demanded the Turks' employers leave Iraq, in a videotape aired on Al-Jazeera television that showed three masked, black-garbed gunmen standing behind two seated men holding various forms of identification, including what were apparently Turkish passports.
Al-Jazeera's newsreader identified the men as two Turkish truck drivers working for a Turkish company delivering goods to U.S. forces in Iraq. The newsreader said the militants threatened to decapitate them if their demands were not met.
It was not immediately clear when the countdown to the 48-hour deadline started.
Militants loyal to al-Zarqawi have claimed responsibility for a number of bloody attacks and beheadings of previous foreign hostages, including U.S. businessman Nicholas Berg, South Korean translator Kim Sun-il and Bulgarian truck driver Georgi Lazov.
Meanwhile, another Turkish driver, Mehmet Dayar, abducted in Iraq on July 17 was freed in Mosul, northern Iraq, after promising his captors not to return, his niece Jihan Dayar told the AP.
Dayar spent 12 days of captivity before returning Thursday to his hometown of Cizre, near the Turkish border with Iraq, she said.
In Fallujah, west of Baghdad, huge explosions were heard late Saturday as fighting resumed in the volatile city between U.S. forces and Iraqi insurgents. Hospital officials said one Iraqi was killed and 19 others, including a child, were injured, while men bellowed through mosque speakers for doctors to go to hospitals and people to donate blood.
In other developments:
In another abduction, a Lebanese citizen was snatched in Baghdad early Saturday, a Lebanese Foreign Ministry officials told The Associated Press, speaking on condition of anonymity. The official said no contact has been made with the kidnappers and had no further details.
Iraqi officials had no immediate comment on the Lebanese man's kidnapping, but an Iraqi man, Hussein Abdullah, claiming to have been kidnapped, beaten and released by armed men told Associated Television Press News that his Lebanese employer had been abducted.
More than 70 foreigners have been kidnapped by insurgents in recent months in a campaign aimed at forcing out of Iraq international troops and companies backing U.S. troops and reconstruction efforts. Many have been videotaped and paraded on TV screens surrounded by hooded militants.
Mediators and officials expressed optimism Saturday for the release of seven hostages - three Indians, three Kenyans and an Egyptian - held captive since July 21. An official from the Kuwait company employing the men met tribal leaders acting as mediators to craft an offer for their captors, and India sent a senior diplomat to help in the talks.
The kidnappers have threatened to kill one of the hostages if their employers, Kuwait and Gulf Link Transport Co., fail to meet their demands, including ending their work in Iraq.
The group, calling itself "The Holders of the Black Banners," had said they would carry out their threat by Friday night, but they had extended their deadlines repeatedly in the past and appeared to have done so again.
India's ambassador to Oman, Talmiz Ahmed, was sent to Iraq on Saturday to help in the negotiations.
Mahdi Saleh, an official from the Kuwaiti company, arrived here Saturday for talks with Sheik Hisham al-Duleimi, who runs an organization of tribal leaders trying to negotiate the hostages' release.
Speaking to Al-Arabiya TV Saturday, al-Duleimi said he expected the militant group to extend its deadline to execute one of the hostages until Sunday as negotiations were progressing well.
"We are in the final stages of the negotiations to release the hostages ... and, God willing, we will be able to save the necks of those seven hostages," al-Duleimi said.
Al-Duleimi's spokesman, Muqam al-Hamadani, told the AP that his group planned to mediate the crisis by crafting an offer with the Kuwaiti company before announcing it to media outlets. He expected the kidnappers to respond by releasing another video to the media, which has been their primary form of communication.
Ram Murti, father of one of the Indian hostages, Antaryami, told the AP in New Delhi that the Indian prime minister's office had phoned him saying the government had received "positive" feedback from Iraq. He didn't elaborate.
Violence resumed in Fallujah on Saturday, with eyewitnesses saying militants and U.S. troops fought in the city's main street and helicopters fired up to eight rockets into an industrial area.
Dr. Osama Abdel Rahman, of Fallujah Hospital, said one Iraqi was killed and seven others were injured. One of the injured was in a serious condition and the others suffered minor injuries.
An official at another hospital, Dr. Hammadi al-Duleimi said 12 wounded people were brought to his medical center.
Earlier Saturday, the U.S. military said 20 insurgents were killed in Fallujah during fighting that began late Thursday and continued until early Friday. Hospital officials said 13 Iraqis died and 14 were injured. The U.S. military and Iraqi security forces suffered no casualties.