Arab television has shown a video tape of a Sudanese interpreter in Iraq who said he had been kidnapped and called on his US employer to leave Iraq.
The man, who identified himself as Noureddin Zakaria of Khartoum, appeared on al-Arabiya TV flanked by armed men.
He said he worked for US firm Titan Corp, and was seized in the rebel stronghold of Ramadi, west of Baghdad.
"I hope and call on the company to stop its operations in Iraq to guarantee my release," he said.
Behind him was a green banner with the words "The National Islamic Resistance, the 1920 Revolution Brigades", the Associated Press reports.
The group has claimed responsibility for attacks around the west Baghdad area.
Titan Corp, is based in San Diego, California, and supplies translators and other information and communication services to the US government. There was no immediate comment from the company.
Meanwhile, a Polish-Iraqi woman who was abducted from her home in Baghdad last week appeared in a video shown on Arabic satellite station al-Jazeera.
"My life is in great danger, and the only thing that will save me is a response to the Iraqis' demand for, first, the withdrawal of Polish military forces from Iraqi territory, and, second, offering any possible help to release Iraqi women prisoners from various US prisons in Iraq," she said, according to an AFP translation of the Arabic voiceover.
The woman has been identified as Teresa Borcz-Khalifa, 54, who was born in Krakow but has been married to an Iraqi and living in Iraq for more than 30 years.
Polish-born Teresa Borcz-Khalifa, in a portrait from her 1978 wedding
The video showed her sitting under the banner of the Salafist Abu Bakr al-Seddiq group.
AFP said the Polish government had immediately rebuffed the demand that it withdraw its 2,500 troops.
The Bangladesh government has also confirmed the identity of one of its nationals taken hostage in Iraq.
Officials said their ambassadors in the Middle East were doing all they could to secure the release of truck driver Abul Kashem.
Mr Kashem, 42, who works for a Kuwaiti transport company, was reportedly seized with a Sri Lankan driver near a US military base by a group called the Islamic Army.
Sri Lankan officials named the kidnapped national as 37-year-old Dinesh Dharmendra Rajaratnam.
The country's foreign ministry said he had been working for a the transport company for more than a year and had recently been sent to Iraq.
There was no fresh news on the fate of British-Iraqi aid worker Margaret Hassan, who was seized more than a week ago on her way to work.