Prime Minister Junichiro Koizumi (search) denounced Iraqi militants threatening to kill Japanese hostages as "cowardly" and vowed Friday to keep Japan's troops in the country despite tearful pleas from the families of the captives.

Television networks repeatedly aired dramatic video of militants holding aid workers Noriaki Imai, 18, and Nahoko Takato, 34, and photojournalist Soichiro Koriyama, 32.

"We want to do everything we can to see that he comes home," said Naoko Imai, whose son, Noriaki, was among the captives. "I want the government to pull the troops out."

Hundreds of demonstrators gathered outside Koizumi's office. But as the drama unfolded and tested Japan's commitment to the U.S.-led coalition — along with potentially threatening Koizumi's political future — there was little he could do except remain defiant.

Koizumi called an emergency meeting of his Cabinet and created a task force to coordinate a response as the drama unfolded and tested Japan's commitment to the U.S.-led coalition.

"We cannot give in to the cowardly threats of terrorists," he said. But he added: "We don't know who this group is. Right now what we need to do is gather accurate information and bring them (the hostages) home safely."

He also ordered a senior foreign ministry official to coordinate rescue efforts from Jordan. Koizumi was expected to make a strong request for help from the United States when Vice President Dick Cheney visits this weekend.

Officials acknowledged, however, there were few other options.

Yasuo Fukuda, the Cabinet's chief spokesman and head of the emergency task force, confirmed the government had "absolutely no contact" with the captors, a previously unknown group calling itself the "Mujahedeen Squadrons." He stressed the withdrawal demand was not under consideration.

"That would be doing just what the terrorists want," he said. "We can't be beaten by them."

Amer al-Husseini, a senior aide to radical Shiite Muslim cleric Muqtada al-Sadr (search), denied Friday that his militia was involved, saying, "We condemn such acts and we pray for their release."

The three were seized in southern Iraq, where al-Sadr's militia, the al-Mahdi Army, has been fighting coalition forces.

In a video obtained by Associated Press Television News, four masked men threaten the blindfolded captives with guns and knives as they lay on the floor of a room with concrete walls. Arab TV network Al-Jazeera also received a copy of the video and said Thursday it came with a statement saying the three would be burned alive if Japan's troops were not removed from Iraq within three days.

The kidnapping has put Koizumi under intense pressure and poses the biggest threat to his pro-U.S. policy on Iraq since two diplomats preparing for the mission were gunned down — possibly by thieves — near the northern Iraqi city of Tikrit in November.

Koizumi's decision to send 1,100 non-combat troops to Iraq in this country's biggest overseas dispatch since World War II has little support from the public, which is wary that Iraq's increasing instability could draw the troops into the line of fire.

That possibility was underscored Wednesday, when mortars exploded near the base housing Japan's troops just outside the southeastern city of Samawah. It was the first attack directed at the base since the Japanese contingent began arriving in Iraq in January. Defense officials confirmed another explosion in Samawah on Thursday but had no further details.

Families of the hostages flew to Tokyo to meet with Foreign Minister Yoriko Kawaguchi.

Nearby, about 600 protesters gathered in front of Koizumi's office, shouting, "Prime minister, don't let the three be killed," and waving banners that read, "Don't lend our hand to the Iraqi occupation."

But many other Japanese continued to support Koizumi.

"Japan should not give in to this kind of terrorism," said Koichi Yoshida, a 43-year-old executive in Tokyo. "Japan has international responsibilities and national interests that are served by the military's presence there."

The deployment has aroused deep sensitivities. Japan kept its troops out of harm's way after its disastrous World War II defeat, and the country's postwar constitution renounces the use of force to settle international disputes.

Koizumi pushed for the deployment to strengthen the alliance with the United States and share some of the burden of ensuring the flow of Middle East oil.

It was a hard sell.

Parliament had to pass special legislation last year to allow the deployment, and the mission was postponed in November after an explosion outside an Italian base killed 32 peacekeepers and Iraqi civilians.

Koizumi faces potential political fallout from the furor in July, when elections are scheduled for the upper house of Parliament.

"This is exactly what we had feared," opposition leader Naoto Kan, head of the Democratic Party, told Parliament. "We had warned that your policy would only foster more terrorism."