The kidnappers of US journalist Jill Carroll have threatened to kill her if US forces do not release all female Iraqi prisoners within 72 hours, according to al-Jazeera television, which broadcast a video of Ms Carroll on Tuesday.
Late on Wednesday, an Iraqi justice ministry official said six out of the eight Iraqi women being detained by US forces were to be freed within days following a review of their case.
Meanwhile, the sister of Interior Minister Bayan Jabr Solagh, who was kidnapped on January 3, a few days before Ms Carroll, was freed, according to Iraqi state television.
Al-Jazeera television broadcast a 20-second soundless videotape showing Ms Carroll, 28, looking tired.
She was seized on January 7 from a western Baghdad street after attempting to meet with a prominent Sunni Arab politician. Her interpreter was shot dead.
Journalists at al-Jazeera said the kidnappers identified themselves as members of a previously unknown armed group calling itself the "Brigades of Vengeance" and threatened to kill her.
"The kidnappers have set the US government a deadline of 72 hours to free Iraqi women prisoners," it said.
Ms Carroll, who freelanced for the Christian Science Monitor, was the 31st media worker to have been kidnapped since the start of the war in 2003, according to Reporters without Borders.
Day of violence
Hours after the video was broadcast two foreign engineers were kidnapped during an ambush on a three-car convoy in a road tunnel in Baghdad, which also left seven Iraqi body guards and three drivers dead.
The convoy belonged to the Iraqna mobile phone company, an interior ministry official said.
Shamel Hanafi, chief commercial officer for Iraqna, told news agency AFP the engineers were from Malawi and Madagascar.
"We don't know whether they were kidnapped, or whether they ran away or are hiding after the attack," he said.
The convoy had been on its way to the western suburb of Abu Ghraib to repair a transmitter station when the attack occurred, officials at the hospital were told.
Meanwhile, two US civilians working for a private security firm were killed and a third wounded by an improvised explosive device that struck their vehicle in the southern city of Basra, the US embassy said.
More than 40 foreigners are being held in Iraq or have been reported missing since a wave of hostage-taking erupted in the war-torn country in 2004. A number of hostages have been killed.