Officials in Tokyo say a body found north of Baghdad is unlikely to be that of a Japanese hostage who has been threatened with execution. Several hours earlier, the government had said that the body resembled that of Shosei Koda.
The body found at Balad, north of the Iraqi capital, was flown to Kuwait Saturday for identification.
Chief Cabinet Secretary Hiroyuki Hosoda told reporters in Tokyo that medical officers at the Japanese embassy in Kuwait examined the body and concluded it did not appear to be that of the 24-year-old Shosei Koda.
Mr. Hosoda says that the height, back of the head and dental structure do not match the description and records of Mr. Koda.
Media reports say the body also appears to be that of someone who died some time ago and had been beaten, tortured and shot.
Foreign Ministry Press Secretary Hatsuhisa Takashima says Japan is asking the U.S. military to confirm whether the body it transferred to Kuwait is actually the same one it told the Japanese government about earlier in the day.
In the pre-dawn hours Saturday, the Foreign Ministry announced that the body, which was found by U.S. troops, strongly resembled Mr. Koda.
In a video recording released on the Internet on Wednesday, militants threatened to behead Mr. Koda unless Japan pulled its troops out of Iraq within 48 hours.
Prime Minister Junichiro Koizumi has said he would not bow to the demands of terrorists.
Japan has about 500 non-combat troops in southern Iraq.
Mr. Koda's family on Friday said they were unaware that he had gone to Iraq. They last heard from him several months ago when he was still studying English in New Zealand, his first overseas trip.
The family appeared on Arabic TV and held a news conference in Tokyo Friday to appeal for Mr. Koda's release, portraying him as an inexperienced traveler with no political intentions but perhaps a desire to help bring peace to Iraq.
The 48-hour deadline passed with no word from the militants holding Mr. Koda. They have identified themselves as followers of Abu Musab al-Zarqawi, who is leading an insurgency against the U.S. military and the Iraq government.