Several thousand guerrilla fighters from Arab countries have flocked to Iraq in the past few weeks to join the battle against U.S. and British forces, with many of them now in the capital engaging in suicidal attacks, senior U.S. officers said today.

Calling themselves mujaheddin, or holy warriors, the Arab fighters have come largely over the border from Syria, sometimes by the busload, according to U.S. military intelligence. In Baghdad in the past few days, U.S. officers said, some of these fighters have stormed into private homes and used them to ambush invading U.S. Army and Marine columns, sometimes hiding behind women and children.

The Arab fighters have come from Egypt, Sudan, Syria, Jordan, Lebanon, Algeria, Morocco, Yemen and the Palestinian territories, according to information collected by U.S. officers from prisoner interrogations and other intelligence.

Three nights ago, a Marine unit captured nine Sudanese fighters, two Syrians and an Egyptian after a firefight on Highway 6 leading into Baghdad, officers said. Most of those taken prisoner so far have been ordinary men with little or no military training, except for some from the Palestinian territories.

Maj. Gen. James N. Mattis, commander of the 1st Marine Division, expressed outrage at the tactics employed by Arab fighters and some of the Iraqi paramilitary members. "They lack any kind of courage," he said. "They literally hide behind women and children, holding them in their houses as they fire. . . . They really lack manhood. They're violating every sense of decency. They're as worthless an example of men as we've ever fought."

It was not possible to interview any of the prisoners. Under the Geneva Conventions, armies that take prisoners of war are not allowed to make them available to journalists.

Armed largely with AK-47 assault rifles and rocket-propelled grenades, the Arab guerrillas are ill-equipped to go up against M1 Abrams tanks or Bradley Fighting Vehicles. However, some U.S. officers fear they will continue to pose a terrorist threat against occupying U.S. troops after the Iraqi government falls.

The precise number of foreign fighters is uncertain. Iraqi officials have claimed that as many as 5,000 Arab fighters have come to their assistance, and prisoners have told U.S. interrogators the same thing. A senior officer interviewed at 1st Marine Division headquarters just outside Baghdad today put the figure at about 3,000.

The arrival of foreigners has strained relations between the United States and Syria, the transit point for most of them. U.S. intelligence concluded that a bus struck near the Iraq-Syria border by U.S. warplanes on March 23 carried Palestinian and other Arab men traveling to Iraq to fight in Iraq's defense. Top U.S. officials have publicly warned Syria not to come to Iraq's aid.

Egyptian President Hosni Mubarak said recently that by invading Iraq the United States risked creating "a thousand Osama bin Ladens." U.S. officers said the guerrillas began coming as soon as war broke out on March 20.

"Some are absolutely devoted to anti-Zionism or anti-Americanism," said a senior officer who asked not to be identified. "Some believe they are coming in solidarity of their Arab brothers." Others were lured under false pretenses, he said. "They thought they were going to get a wife. . . . A lot of these guys, this isn't what they signed up for, and they're pretty upset. They were forced to fight."

U.S. intelligence detected dozens of Arab volunteers arriving March 31 in Basra, Iraq's second-largest city, located in the southeast. They came from Algeria, Morocco, Syria and Yemen to fight British troops.

In some small towns and along the highways between Kuwait and Baghdad, Arab fighters in pickup trucks have fired assault rifles at tanks and armored vehicles, despite the near certainty of being killed by superior firepower. The U.S. armored vehicles just mow down the attackers, officers said.

Some U.S. soldiers and Marines are surprised to see some of the foreign attackers get up after a machine-gun burst and continue the charge until they too are mowed down.

More recently, the Arab guerrillas have made their way to Baghdad, with most of them coming from Yemen and the militant Lebanese group Hezbollah, according to U.S. intelligence.

Marine officers said they hope to stanch the flow of arriving foreigners with quick and decisive military victories in Baghdad. "I think these guys are wrapped up in the moment," said Lt. Col. David Pere, senior watch officer at Marine headquarters, "and as soon as reports of wholesale destruction . . . get back [saying] that the forces that were sent are never coming home, I imagine that will stop the flow."

Other officers said they were eager to kill as many of the foreign guerrillas as possible in Iraq because it will prevent terrorist attacks on civilian targets elsewhere. "They should send every volunteer they can think of here," said Col. Larry Brown, the chief operations officer for the Marines in Iraq. "Let me get 'em all at once. It'll simplify my task later."

Arab volunteers in support of Iraq removed their dead in a pickup truck after fierce fighting with U.S. troops south of Baghdad on Sunday.