Two foreign engineers working for Iraqna, an Iraqi branch of the Egyptian mobile firm Orascom, were also reported missing.
Earlier, the kidnappers of a female journalist from the United States, Jill Carroll, threatened to kill her unless the United States frees Iraqi women prisoners within 72 hours.
The Arabic television channel Al-Jazeera broadcast a brief video showing Carroll, who was working for the U.S. newspaper "The Christian Science Monitor" when she was abducted at gunpoint in Baghdad on 7 January.
A previously unknown group calling itself the Brigades of Vengeance has apparently claimed the abduction.
The U.S. State Department said Washington is making every effort to secure Carroll's release as soon as possible.
A U.S. military spokesman, Lieutenant Aaron Henninger, said on 18 January that U.S. American forces are holding eight women prisoners in Iraq, adding that they were a threat to security.