China says it is taking "all measures" to secure the release of eight of its nationals abducted in Iraq.
The hostages were shown holding up their passports
Government spokesman Kong Quan said the men went to Iraq individually in search of work and, having failed, were returning home when they were abducted.
A group calling itself Numan Brigade released a video of the men and said they were employed by a construction company working with US troops.
It called on China, an opponent of the war, to clarify its role in Iraq.
Mr Kong told reporters in Beijing that the Chinese government was deeply concerned by the abduction of the men.
"China's Foreign Ministry is taking all measures to rescue the hostages," he said.
He described the men as ordinary Chinese citizens who had arrived separately in Iraq in the hope of finding work.
Having failed, they had hired a car to take them out of the country when they were seized.
Apparently contradicting the spokesman's statement, the official Xinhua news agency quoted sources saying that the men had been working on a Chinese project to rebuild a factory in Najaf - a project which Xinhua said had nothing to do with the US-led multinational forces.
The insurgents released a videotape of the Chinese men holding their passports.
They said the hostages would be shot within 48 hours unless Beijing "clarifies its role" in Iraq.
But the Associated Press news agency said that the group's statement suggested the men could be freed, as long as they did not return to work for "occupation forces" in Iraq.
China was strongly opposed to the US-led war in Iraq.
Mr Kong said the Chinese government had always placed emphasis on the protection of the Iraqi people's basic interests.
"The Chinese people has always cherished friendly feelings towards the Iraqi people and sympathised and supported them," he told reporters.
More than 120 foreigners have been taken hostage in Iraq since the US-led occupation began in 2003.