A new U.S.-led operation is under way to eliminate the al-Mahdi Army militia, led by the anti-American radical Shiite (search) cleric Muqtada al-Sadr (search).

Operation Resolute Sword will aim to break the hold the militia has over some parts of three southern Iraqi cities as U.S. Marines and Iraqi soldiers continue to battle insurgents in Fallujah and other cities.

In escalating violence against foreign civilians, insurgents kidnapped three Japanese, eight South Koreans and two Arab aid workers from Jerusalem.

The militia led by al-Sadr has full control over the city of Kut and partial control in Najaf, but coalition forces will move soon, said Army Lt. Gen. Ricardo Sanchez (search), the top U.S. general in Iraq. Residents of Kufa said Thursday militiamen also control that southern city by holding police stations and government buildings.

In a videotape broadcast to the Arab world by Al-Jazeera, captors armed with automatic rifles and swords threatened to kill the blindfolded Japanese hostages unless Tokyo removed its troops from Iraq. Japan said it had "no reason" to withdraw.

Iraq's interior minister, who leads police and security forces, resigned at the request of top U.S. administrator, L. Paul Bremer, to maintain balance between Sunni and Shiite factions on the governing council. It was unclear if the resignation of Nuri al-Badran was also connected with the failure of Iraqi police to confront insurgents that coalition forces are battling on two fronts.

Sanchez said there appeared to be links "at the lowest levels" between the Shiite militia — which has been battling coalition forces in at least a half-dozen southern cities this week — and Sunni Arab insurgents who have long fought U.S. troops in central Iraq cities such as Fallujah and Ramadi.

Ukrainian troops were forced to withdraw from their bases in Kut on Wednesday, but Sanchez said coalition forces would retake it "imminently."

He suggested the presence of hundreds of thousands of Shiite pilgrims in Najaf for a religious occasion this weekend was hampering coalition forces from moving against militiamen there.

"We are very cognizant of the religious ceremonies," he said.

Polish and Bulgarian soldiers drove off Shiites who attacked them near the municipal hall in Karbala south of Baghdad during all-night battles, a Polish spokesman said.

Coalition forces suffered no casualties but killed nine attackers and wounded about 20 others, Lt. Col. Robert Strzelecki said in an interview from Iraq.

The attacks began about 11 p.m. Wednesday and continued until nearly sunrise, Strzelecki said. The attackers, loyal to al-Sadr, used machine guns, rocket-propelled grenades and small arms during fighting that the spokesman described as heavy.

In the Sunni Muslim stronghold of Fallujah, U.S. Marines fought insurgents for a second day. One U.S. Marine was reported killed by the military, although it released no details.

Marines battled again around the Abdel-Aziz al-Samarrai mosque, which Capt. James Edge said insurgents were again using as a base despite a six-hour battle Wednesday to uproot them. Helicopters were deployed to support the Marines, he said.

Capping Wednesday's battle, a U.S. Cobra helicopter fired a missile at the base of the mosque's minaret, and an F-16 dropped a laser-guided bomb at the wall, allowing Marines to move in and seize the site, Lt. Col. Brennan Byrne said.

Fighting this week in Fallujah, Ramadi and elsewhere has left 36 Americans and at least 459 Iraqis dead. The director of the city's hospital, Taher Al-Issawai, said the figure included more than 280 Iraqis killed since the Marines' siege against insurgents in Fallujah, west of Baghdad, began early Monday.

The kidnappings represented a new tactic targeting foreigners in Iraq in order to pressure their governments, which are allied with the United States. It could affect U.N. workers, journalists, aid workers, Christian missionaries, security personnel and those doing business with the Iraqi government.

Lawmakers in Tokyo said the Japanese civilians — identified as two male journalists and a female aid worker — were kidnapped by a terrorist-related group, according to the Japanese news agency Kyodo.

Chief Cabinet Secretary Yasuo Fukuda said the government was still trying to confirm the reports about the hostages, but he added that Japan was standing firm in its commitment to Iraq, adding there was "no reason" to withdraw.

In the videotape, obtained by The Associated Press, three Japanese were shown blindfolded and crouched on the floor of a concrete walled room with an iron door standing behind them are four masked gunmen in black, holding automatic weapons and rocket-propelled grenade launchers.

The gunmen made the Japanese lie on the floor, pointing swords and knives at their chests and throats. The woman's lips could be seen moving as if she was speaking.

One gunman put a knife to the throat of a man, whose eyes widened in panic, and he struggled against his captor. The woman wept and hid her eyes as another gunman tried to pull her hands away from her face and he pressed a knife toward her throat.

The video also showed the captives' passports.

Tokyo has sent 530 ground troops to the southern city of Samawah, part of a planned deployment of 1,100 on a noncombat mission to purify water and help rebuild Iraq — Japan's first deployment of troops since World War II.

Japanese Prime Minister Junichiro Koizumi has been one of the strongest backers of the U.S.-led invasion, a stance that has raised concern Japanese troops could be targeted by insurgents.

The Japanese were taken by a group identifying itself as the "Mujahedeen Squadrons," which Al-Jazeera said gave a three-day ultimatum for Japan to announce it will withdraw its troops or they would be killed.

The eight South Koreans were detained by unidentified "armed men," but one was later released, a Foreign Ministry official in Seoul told AP, speaking on condition of anonymity.

The eight evangelical Christians left in two cars on April 5 from Amman, Jordan, when they were seized about 155 miles east of Baghdad, said the escapee, identified by South Korea's Yonhap news agency as Kim Sang Mik, from a church in Incheon.

Yonhap did not say how Kim escaped. The South Korean Foreign Ministry told the AP it did not know who was responsible for the capture.

Earlier this week, two South Korean aid workers were briefly detained by Shiite forces in a gunbattle with Italian peacekeepers. They were released unharmed.

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

Israeli media reported, meanwhile, that two Arab residents of Jerusalem — including one with a U.S. driver's license from the state of Georgia who works for an American aid agency — were kidnapped Thursday by insurgents in Iraq, although the Israeli Foreign Ministry could not confirm the report. It was unclear whether the two were Israeli citizens.

The Iranian TV report, rebroadcast in Israel, showed men identifying themselves as international aid workers Nabil Razouk, 30, and Ahmed Yassin Tikati, 33.

The report showed photos of their documents, which included Razouk's Georgia driver's license and an Israeli driver's license.

His uncle, Anton, told the AP that his nephew was an Israeli citizen with an Israeli passport who was working for the U.S. Agency for International Development. An Arab Christian, Razouk lives in east Jerusalem and is married to a Czech, Anton Razouk said.

"I am very worried. I pray for his safety," Anton Razouk said.

"I want to tell the Iraqis he is not a spy, not for America and not for Israel," he said. "He is an Arab, a member of the Arab nation, a Palestinian like me living in Jerusalem under Israeli occupation."

Also Thursday, three explosions were heard in central Baghdad. A coalition spokeswoman said the blasts were the result of controlled detonations of seized ordnance.

The Associated Press contributed to this report.