Islamic militants had threatened on Tuesday to kill hostage Shosei Koda within 48 hours unless Japan withdrew its troops from Iraq. Prime Minister Junichiro Koizumi firmly rejected that demand, saying he would not give in to terrorists.
Kyodo said a body found in the city of Tikrit, Iraq, had been identified as Koda. The report could not be immediately confirmed early Saturday.
The ranks of foreign hostages in Iraq have grown again, with the kidnapping of a Polish woman in her 60s who is married to an Iraqi. Her captors are demanding that Poland withdraw its 2,400 soldiers and that the U.S.-led coalition free all Iraqi women held at Abu Ghraib prison.
President Aleksander Kwasniewski said Poland will not surrender "to the dictate of terrorists" by meeting the demands. Poland commands some 6,000 troops from 15 nations in three provinces south of Baghdad.
In other recent developments:
The Polish hostage, in a video on Al-Jazeera television, is seen sitting in front of two masked men, one of whom was pointing a pistol at her head.
She is identified as Teresa Borcz-Kalifa by one of her former employers at the Polish Embassy in Baghdad, where she worked in the 1990s. Leszek Adamiec told Poland's private Radio Zet that Borcz-Kalifa worked in the consular section until 1994.
Borcz-Kalifa, a longtime resident with Iraqi citizenship, is believed to have been abducted Wednesday night from her home in Baghdad.
She is the ninth foreign woman abducted in Iraq since a wave of kidnappings began last spring. By comparison, Iraqi officials say that at least 152 Iraqis have been kidnapped this month - the highest monthly total since the occupation began last year.
A terror group calling itself the Abu Bakr al-Siddiq Fundamentalist Brigades has claimed responsibility for Borcz-Kalifa's abduction.
Her voice is not audible on the tape, but Al-Jazeera said she urged Polish troops to leave the country and for U.S. and Iraqi authorities to release all female detainees from Abu Ghraib. The kidnappers did not mention a specific death threat or give a deadline.
All but two foreign women hostages have been released, and in a statement issued Thursday in London, CARE International appealed for the release of Margaret Hassan, a British-Irish-Iraqi citizen who has headed the humanitarian organization's operations in Iraq since 1991.
"CARE has closed down all operations in Iraq," the statement said in English and Arabic. "Please release Mrs. Hassan to her family and friends in Iraq."
No group has claimed responsibility for kidnapping Hassan, but in a video aired Wednesday she is seen pleading for the withdrawal of British troops and the release of Iraq women prisoners.
Several groups of hostage-takers have demanded the release of women prisoners in Iraq, including al-Zarqawi's organization. Two Americans and a Briton were beheaded last month after coalition forces refused the demand.