An Islamist militant group in Iraq has threatened to kill a Japanese citizen it has taken hostage if Tokyo fails to withdraw its troops from the country.
The militants force Koda to look at the camera at one stage
The al-Qaeda in Iraq group led by Abu Musab al-Zarqawi released a video broadcast on an Arabic TV station which shows the hostage and three masked men.
Addressing Japan's premier, the hostage says his captors want to behead him.
Responding to the 48-hour deadline issued by the group on Tuesday, Tokyo has refused to meet the demand.
"We cannot tolerate terrorism and we will not give in to terrorism - we will not withdraw..." said Japanese Prime Minister Junichiro Koizumi.
The man has been identified as Shosei Koda, 24, from Fukuoka Prefecture. Mr Koda left Japan on a backpacking holiday in January and it appears that he entered Iraq from Jordan by bus to do some sightseeing.
The Japanese government has appealed for Mr Koda's release, insisting he has no links to the military.
'Berg and Bigley'
The video shows Mr Koda kneeling in front of three masked men, who describe him as "an element connected to the Japanese armed forces".
"They asked me why Japanese government broke the law and sent troops to Iraq," Mr Koda, wearing a white t-shirt, says in broken English.
Hostage Shosei Koda says his captors are prepared to kill him
"They want to withdraw the Japanese troops from Iraq or cut my head."
He then says in Japanese: "Mr Koizumi... I'm sorry to put my head in your hands. I want to return to Japan."
One of the militants, who are identified by a black banner as members of al-Qaeda in Iraq group, then reads out a statement over the kneeling man.
"We give the Japanese government 48 hours to withdraw its troops from Iraq, otherwise his fate will be the same of that his predecessors, Berg and Bigley and other infidels," he says, referring to previous hostages beheaded by militants.
As the militant speaks, another grabs the captive by the hair and forces him to face the camera.
Al-Jazeera TV, which showed the video, said it had been posted on a website.
'I'll be just fine'
Japanese Foreign Minister Nobutaka Machimura appealed for Mr Koda's release, saying Japan was "Iraq's friend".
"The grief of the family of Mr Koda in particular is indeed profound," he added.
Mr Koda's father told broadcaster NHK his son had left Japan in January and started a working holiday in New Zealand in July.
The 24-year-old, thought to have been working at a hotel in Jordan, had not told his family he planned to go to Iraq.
A documentary filmmaker, Hiroshi Shinomiya, told NHK that he had met him at a hotel in the Jordanian capital, Amman, on 19 October.
Mr Koda had told him he planned to take a public bus the next day to Iraq
"simply because he wanted to see it" and said he would be "just fine" when Mr Shinomiya tried to dissuade him.
A crisis centre has been set up at the Japanese prime minister's office to discuss the country's reaction and Deputy Foreign Minister Shuzen Tanigawa has left for Jordan in a bid to negotiate Mr Koda's release.
Three Japanese citizens were taken hostage in Iraq in April, but later freed.