The "Army of Islam" group on Wednesday said it was holding a Jordanian and warned Iraqis, Arabs and other foreigners against cooperating with the occupiers.
No further details were immediately available.
There was no immediate word from Jordan, which has extensive trade and economic ties with Iraq.
Different groups have seized dozens of foreigners to pressure allies of the United States and foreign firms and expatriate workers to leave Iraq.
Many have been released but about 25 have been killed.