In a dramatic video released Thursday, insurgents revealed they had kidnapped three Japanese and threatened to burn them alive in three days unless Japan agrees to withdraw its troops from Iraq.

Armed with assault rifles and rocket-propelled grenades, the kidnappers shouted "Allahu akbar" -- God is great -- in the video and held knives to the throats of the Japanese, who screamed and whimpered in terror.

Japan's government said it has no plans to pull troops out of Iraq in response to the threat, which came amid a series of other kidnappings targeting civilians.

Two Arab residents of east Jerusalem -- one an Israeli citizen working for a U.S. aid group -- and seven South Korean Christian missionaries (search) were detained Thursday, though the Koreans were released.

A Canadian humanitarian aid worker for the International Rescue Committee was taken hostage Wednesday by a local militia in Najaf, southern Iraq, the agency said Thursday. Fadhi Ihsan Fadel was the first Canadian to be abducted in Iraq, Canadian Foreign Affairs spokesman Sameer Ahmed said in Toronto.

The events suggested a new tactic by insurgents to pressure the governments of Washington's allies in Iraq, and posed dire implications for U.N. workers, journalists, religious groups, security personnel and other civilians doing business here.

Foreigners have been detained by gunmen for brief periods in the past -- usually in robberies -- and Iraqi citizens have been kidnapped and held for ransom by criminals. But this was the first time foreigners have been snatched for political reasons, and the first such dramatic video ultimatum.

The Arabic TV station Al-Jazeera, broadcasting to Iraq and the rest of the Arab world, aired portions of the video of the Japanese hostages released by a previously unknown group calling itself the "Mujahedeen Squadrons." It showed two men and one woman surrounded by gunmen wearing black, and close-ups of the captives' passports.

Al-Jazeera editors said the three were taken hostage in southern Iraq, where black-clad Shiite (search) militiamen have been engaged in an uprising this week. The exact date of their capture was not known.

Japanese troops are based outside the southern Iraqi city of Samawah.

Associated Press Television News obtained a copy of the full video, in which four masked men point knives and swords at the blindfolded captives as they lie on the floor of a room with concrete walls.

At one point, a gunman holds a knife to the throat of one of the men, whose blindfold has been removed; his eyes widen in panic and he struggles to try to get free. The woman screams and weeps.

On Al-Jazeera, an announcer read a statement he said came with the video declaring a three-day ultimatum for Japan to announce its withdrawal of troops.

"Three of your sons have fallen into our hands," the announcer read. "We offer you two choices: either pull out your forces, or we will burn them alive. We give you three days starting the day this tape is broadcast."

Japan's NHK television identified the captives as two aid workers and a journalist. The passports shown in the video belong to Noriaki Imai, born 1985; Soichiro Koriyama, 32; and Nahoko Takato, 34. The gunmen also displayed a press card for Koriyama from the weekly newspaper Asahi.

Fadel, the Canadian aid worker, is a 33-year-old who was born in Syrian, the IRC said. He manages a UNICEF-funded program that provides humanitarian assistance for vulnerable children and youth in southern Iraq, the New York-based IRC said in a statement on its web site.

Those activities included the rehabilitation of a youth center, the distribution of wheelchairs to injured children in Najaf and support to local schools, the IRC said.

The South Korean missionaries were stopped by armed men at a checkpoint on a highway from Amman, Jordan, to Baghdad. The eight Koreans were traveling in two cars to attend the opening of a missionary school near the northern city of Mosul, Seoul officials said.

The gunmen dragged seven of the missionaries from the vehicles and seized their passports. The eighth said she escaped when the Iraqi driver of her car drove off before she could get out.

Freed after about nine hours, one of the missionaries, a middle-aged man, told APTN in Baghdad that the captors, who wore masks, treated them well.

"First, I felt insecure, but later they made us feel comfortable and gave us food and drinks," the man said. "I think at first they thought we were linked to U.S. soldiers."

News of the kidnappings of the two Arabs came in video footage from Iranian television, rebroadcast on Israeli television. It shows images of the men's documents, including an Israeli driver's license, a health insurance card and a supermarket card. A U.S. driver's license from the state of Georgia also was displayed.

The men identify themselves as Nabil Razouk, 30, and Ahmed Yassin Tikati, 33.

An uncle of Razouk told AP his nephew had an Israeli passport and worked for the U.S. Agency for International Development (search). Razouk is a Christian and is married to a Czech woman, Anton Razouk said.

He pleaded for his nephew's safety in an APTN interview. "I want to tell the Iraqis he is not a spy, not for America and not for Israel," the uncle said. "He is an Arab, a member of the Arab nation, a Palestinian like me living in Jerusalem under Israeli occupation."

Japan has about 530 ground troops in Samawah, part of a total planned deployment of 1,100 soldiers for a mission to purify water and carry out other reconstruction tasks.

About 460 South Korean medics and military engineers have been in Nasiriyah for almost a year. They are to come home after South Korea's planned deployment of 3,600 more troops to the Kurdish region of northern Iraq later this year.