Baghdad, Iraq ? An Islamic militant group announced Wednesday that it had captured six civilians from India, Kenya and Egypt and threatened to behead them unless their countries withdraw all workers from Iraq.

The hostages were shown on a televised videotape, lined up behind their masked and armed captors. The Egyptian briefly pleaded for help.

The threat came one day after a Filipino civilian was released unharmed in Baghdad after two weeks in captivity when the Philippines, in a move criticized by other governments, met the demands of his kidnappers by pulling its 52 troops out of multinational military operations here.

It also came as new clashes were reported in the city of Ramadi, 30 miles west of Baghdad, between armed insurgents and U.S. Iraqi police reported that a U.S. military helicopter had been shot down there, but a spokesman for the U.S. Marine Corps in Iraq denied it.

Meanwhile, a car bomb exploded Wednesday in eastern Baghdad afternoon, killing at least four people, and an American soldier was killed by a roadside bomb while on patrol in a town 45 miles north of the capital.

None of the new hostages’ countries has troops stationed in Iraq, but the kidnappers, who called themselves The Hoisters of the Black Flags, demanded that the three governments recall all workers and also that Kuwait shut down its offices in Iraq within 72 hours, or they would begin executing the men.

“We have warned all countries, companies, businessmen and truck drivers that those who deal with the American cowboy occupiers will be targeted by the fires of the mujaheddin,” the group said in a separate statement sent to the Associated Press.

The workers appear to be employed by a Kuwaiti trucking firm, Universal Services. In the videotape shown on al-Arabiya television, they held up a sheet of paper that looked like an employment roster.

There was no immediate reaction from the four concerned governments.

“How are we going to feed our families? We ask the company to do something and take us back to our countries,” the Egyptian captive, identified as Mohammed Ali Sanad, said in Arabic during the brief tape. The other shirtsleeved captives stood silently, their faces grim and worried.

Three insurgents carrying automatic weapons stand in front of six hostages in this picture handed to the Associated Press in Iraq. A militant group says it will behead them if their countries do not withdraw their workers.

In two separate threats sent Wednesday over an Islamic Web site, other groups demanded that Poland, Bulgaria and Japan withdraw their troops from Iraq. One group vowed to launch deadly attacks in the first two countries, similar to those that destroyed the World Trade Center in New York and a train station in Madrid.

“To the crusader Bulgarian government … we demand, for the last time, that you withdraw Bulgarian troops out of Iraq or we swear we will turn Bulgaria into pools of blood,” said the on-line statement from a group calling itself al-Qaida in Europe. A statement on the same Web site, but from a different group, urged Japan to follow the steps of the Philippine government.

“To the government of Japan: Do what the Philippines has done. By God, nobody will protect you ,” the warning said. “Lines of cars laden with explosives are awaiting you. We will not stop.” The statement purported to be from a group affiliated with Jordanian guerrilla Abu Musab al-Zarqawi, but its authenticity was not confirmed.

All three governments immediately rejected the demands, saying they would keep their forces in Iraq. An official in Japan’s Foreign Ministry said the 500 Japanese troops in Iraq would continue their medical and reconstruction mission.