The Japanese government scrambled Wednesday to win the release of a 24-year-old Japanese man taken hostage in Iraq, dispatching senior diplomats to the Middle East and appealing for his freedom on Arabic television.

But Prime Minister Junichiro Koizumi said Japan would not grant the kidnappers' demand for the withdrawal of its 550 troops from southern Iraq, where they are helping with reconstruction. "We cannot tolerate terrorism and we will not give in to terrorism," Koizumi told reporters in Tokyo.

Foreign Minister Nobutaka Machimura appeared on the al-Jazeera satellite television network, requesting the release of Shosei Koda and reiterating the humanitarian role of Japanese troops in Iraq.

"The people of Japan are shocked and are hoping for the release of the hostage as soon as possible," Machimura said in a separate statement issued in Tokyo. "The grief of the family of Mr. Koda in particular is indeed profound."

Koda, described as an adventure traveler from the southern Japanese island of Kyushu, was shown pleading for his life in a video posted on a radical Islamic Web site Tuesday and broadcast Wednesday on national television in Japan.

Under a sign bearing the name of a group led by Abu Musab Zarqawi, a Jordanian-born militant leader in Iraq, the hooded kidnappers threatened to behead Koda if Japanese troops did not leave within 48 hours.

Public opposition to the Iraq mission, Japan's largest military operation abroad since World War II, runs deep. Some analysts say Koizumi may now come under renewed pressure to withdraw the troops, especially if the kidnappers behead Koda, as they have other foreign hostages in recent months.

Five Japanese civilians kidnapped in two separate incidents in April were later released unharmed after mediation by Iraqi clerics. Koda is the first Japanese seized by followers of Zarqawi, who have asserted responsibility for many of the beheadings in Iraq.

"The situation is critical -- this group of hostage-takers is bad," Soichiro Koriyama, a Japanese freelance journalist who was among those taken hostage in Iraq, said in a telephone interview. "This is different, worse than our hostage situation. There is a 48-hour time limit and we're running out of time."

Koda's distressed parents confirmed that the man seen on the video was their son, saying they had last seen him when he left home 10 months ago for a year in New Zealand, reportedly to study English. "We hope he will come back as healthy as he left," his father, Masumi Koda, a carpenter, said in a televised statement. "We pray that he will be saved."

Hiroshi Shinomiya, a Japanese movie director filming in the Middle East, told reporters that he had met Koda in Amman, Jordan, after the young man had apparently spent two months working in Israel for extra cash. Koda said he planned to visit Iraq out of curiosity, Shinomiya said, and rejected the director's attempts to talk him out of the trip. Koda checked out of the Cliff Hotel in Amman on Oct. 20, heading for Iraq.

A man resembling Koda was seen wandering around the Karrada district in central Baghdad several days ago wearing shorts and tennis shoes and carrying a light backpack. Because of the threat of kidnapping, foreigners rarely walk on the streets of the capital anymore and stand out when they do.

In the video, Koda's captors suggested he was somehow linked to Japan's military. Japanese officials denied that Wednesday, calling him a private citizen.

Machimura expressed frustration with Koda's decision to visit Iraq. "It is truly hard to understand why he traveled, despite repeated strong evacuation advice and being fully aware that it is dangerous there," the foreign minister said.

Looking terrified in the video, Koda appeared to apologize for his capture. "Mr. Koizumi, they are calling on the Japanese government to withdraw Japan's Self-Defense Forces," Koda said in Japanese. "They are saying they will cut off my head otherwise. I am sorry. I want to return to Japan again."

Staff writer Jackie Spinner in Baghdad and special correspondents Akiko Yamamoto and Sachiko Sakamaki in Tokyo contributed to this report.

Shosei Koda, 24, described as an adventure traveler, pleaded for his life on video posted on the Internet.