Armed men wearing military fatigues seized two German engineers from a car in northern Iraq on Tuesday in the latest brazen kidnapping to push a foreign government into another desperate race to free its nationals.

Efforts continued to rescue Jill Carroll, the American freelance reporter kidnapped Jan. 7 in Baghdad. Carroll's appearance last week on a silent videotape aired on Arab TV marked the only sign of her since her abduction.

More than 250 foreigners have been kidnapped in Iraq since the 2003 U.S.-led invasion that toppled Saddam Hussein, and at least 39 have been killed.

The German government confirmed that two young German males from Leipzig were kidnapped Tuesday and said a special crisis team was sent to Iraq to deal with the matter. Foreign Minister Frank-Walter Steinmeier said Berlin was doing "everything in our power so that we not only receive information, but the hostages will be returned to us safely."

The hostages worked at an Iraqi state-owned detergent plant, near the oil refinery in Beiji, 155 miles north of Baghdad. German media said they were employed by Cryotec Anlagenbau GmbH, a manufacturing and engineering company involved in Iraq since before the 2003 war.

Police Capt. Falah al-Janabi said gunmen using two cars and wearing military uniforms pulled the Germans out of a car while they were heading to work.

Another policeman, who declined to be identified for fear of being targeted by insurgents, said two Iraqi men, apparently co-workers, were in the same car as the Germans when at least four militants brandishing semiautomatic weapons stopped them.

The kidnappers bundled the Germans into two cars and sped away, leaving the two Iraqis behind, the policeman said.

Police searched for the hostages by erecting checkpoints throughout the area, where Brazilian engineer Joao Jose Vasconcelos Jr., was also kidnapped on Jan. 19, 2005. Vasconcelos' whereabouts remain unknown.

Meanwhile, hundreds of Shiite Muslims in the southern city of Basra demanded British troops free Iraqi policemen arrested Tuesday in connection with multiple militia-linked assassinations.

In the northern city of Samarra, about 1,000 Sunni Arabs marched to condemn the execution-style killings of 31 Sunnis abducted after being rejected from a police academy.

The U.S. military said four American military personnel were killed in separate incidents on Monday — two soldiers in a Baghdad roadside bombing and two Marines in a vehicle accident west of the capital.

The number of U.S. troops in Iraq has been cut to the lowest level since last summer, when a buildup for election protection expanded the force to about 160,000, Pentagon officials said Tuesday.

There are now about 136,000 troops in Iraq, according to Lt. Col. Barry Venable, a Pentagon spokesman. He said this meant that the extra forces in place during the October constitutional referendum and the December parliamentary elections have been removed and a rotation of major combat units has largely been completed.

Car bombs and mortar fire rumbled throughout Baghdad on Tuesday ahead of the planned resumption of Saddam's trial on accusations of playing a role in the 1982 killing of more than 140 Shiite Muslims.

But the case was postponed to Sunday amid turmoil over the last-minute replacement of the top two judges on the five-member panel and claims several witnesses were still in Saudi Arabia where they had been performing a Muslim pilgrimage.

A spate of kidnappings and killings targeting Sunni Arabs in recent days also cast a pall over delicate negotiations to form a national unity government of Shiites, Sunni Arabs and Kurds.

A major Sunni clerical group, the Association of Muslim Scholars, blamed Shiite-dominated Interior Ministry forces for a Monday raid in Baghdad's Sunni neighborhood of Toubji in which three men were killed and more than 20 abducted.

Another leading Sunni Arab group, the Iraqi Islamic Party, warned its followers to be prepared to confront further armed attacks "by any suitable means."

"Any pretext by the government is unacceptable, so we call upon all reasonable Iraqis to do their best to stop the bloodshed and prevent more deterioration in security," said a statement released by the party. The group is a partner in the Sunni Iraqi National Accordance Front that won 44 of the 275 seats in last month's election.