FALLUJAH, Iraq -- American officers waging a major counterinsurgency campaign in Iraq say that the murky identity of their attackers is slowly coming into focus, and what they see is troubling.

The continuing anti-U.S. violence in the central part of the country, they say, appears to be the work of an unlikely but deepening alliance between two of Iraq´s most mutually antagonistic subcultures: secular Baath Party militants and Islamic extremists united only by a burning hatred of America.

The militants, who have been staging an increasingly deadly series of ambushes against U.S. troops in recent weeks, shot another American soldier Monday in Baghdad, the U.S. Central Command said. The soldier, from Indiana, died of his wounds early Tuesday.

And in an ominous new twist to the armed resistance in the country, Iraqi guerrillas for the first time appear to be attacking local officials and institutions that are collaborating with occupation forces. On Monday night, gunmen in cars tossed grenades at Fallujah´s courthouse and mayor´s office, the focus of U.S. reconstruction efforts in the hostile town. There were no reports of casualties.

"The standard wisdom is that the attackers are die-hard Baathists who have reorganized and formed underground cells," said Maj. Joffery Watson, the intelligence officer for the 2nd Brigade, 3rd Infantry Division, which is policing Fallujah.

"But the fundamentalists are gaining influence," Watson said. "The Baathists offer their military skills, but the mosques are the rallying point. They´re the staging grounds for the attacks."

More than 370 Iraqis have been arrested since Sunday in a security sweep code-named Operation Desert Scorpion, the second major counterinsurgency campaign in Iraq in two weeks, the U.S. military said.

Nighttime raids

Scores of nighttime raids and random checkpoints have resulted in the arrest of 215 suspected militants in the northern cities of Tikrit and Kirkuk over the past 72 hours, Central Command said. About 150 people were detained in Baghdad, and 121 rifles, 18 rocket-propelled grenades and 31 pounds of explosives also were seized.

The security crackdowns are a response to a series of increasingly deadly ambushes against U.S. forces in recent weeks. They are designed to "isolate and defeat pockets of resistance that are seeking to delay the transition to a peaceful" Iraq, Central Command said.

At least 50 U.S. soldiers have died from sniping, ambushes or accidents since major fighting ended in Iraq in April--more than a quarter of all the deaths during the war´s combat phase.

Shot while in vehicle

The latest soldier killed was Pvt. Shawn Pahnke, 25, of Shelbyville, Ind., who was shot late Monday afternoon as he sat in his vehicle in northwest Baghdad, Central Command said.

So far, the U.S. operations have focused on the central and northern parts of the country, which are viewed as traditional strongholds of deposed dictator Saddam Hussein. And the classic case study is Fallujah.

A sullen farming town 37 miles west of Baghdad, Fallujah was one of the first Iraqi communities to openly resist American forces after Baghdad fell in April. Relations between U.S. soldiers and local residents soured six weeks ago when troops with the 82nd Airborne Division fatally shot 14 civilians during a protest march. The U.S. troops said they responded after taking fire.

Today, officers trying to police the town say the residents´ penchant for springing ambushes, sniping from mosques and signaling one another with porch lights and flares offers perhaps the best example of how the merging forces of nationalism and religion are coming to define the nascent insurgent movement in central and northern Iraq.

"Many of those planning [the attacks] are Baathists, ex-army guys who´ve lost their perks with the fall of the old regime," said Capt. James Brownlee, a spokesman for the 3rd Infantry Division. "We´re talking about cells of 10 officers or Fedayeen Saddam militants who´ve got their act together locally."

But according to U.S. intelligence, that act increasingly revolves around some of Fallujah´s 46 mosques.

Militants have been spotted surreptitiously moving weapons into key mosques, said Watson, the 3rd Infantry Division intelligence officer. Ambushes against U.S. patrols erupt in the same neighborhood later, he said.

The tactic is effective because U.S. forces hesitate to raid mosques for fear of outraging Fallujah´s conservative populace. Two attacks have come directly from mosques over the past six weeks, Watson said. Mosques also have been used to either hide militants or store arms in Mosul and Baghdad, U.S. military sources said.

"We used to think ´Islamist versus Baathist´ attackers," Watson said. "Now the picture we´re getting is that they´re cooperating. They´re one and the same."

Citing information from captured insurgents, he described a typical ambush operation in Fallujah: "A few military guys get their explosives on Thursday. They go to prayer services on Friday. The imam whips them up with some inspirational jihad rhetoric. And--boom-- we´ve got an attack near the mosque Saturday night."

Such interaction would have been unthinkable before the war that toppled Hussein, whose repressive Baath Party was built on a secular, Soviet-style ideology.

Though the Iraqi dictator embraced the symbols of Islam to boost his popularity during the last years of his rule, he ruthlessly snuffed out challenges from religious fundamentalists.

Rebellious imams from Iraq´s Shiite Muslim majority were executed, imprisoned or exiled. Even clerics from Hussein´s Sunni sect were carefully vetted and often silenced with threats or bought off.

Most conservative Islamists held Hussein in contempt. The most famous, Osama bin Laden, considered Hussein´s Iraq a godless, corrupt cesspool.

"The religious element saw an opportunity to co-opt the resistance movement during the postwar chaos," Watson said. "To a large degree, they succeeded."

The imams at two mosques in Fallujah refused to comment. One of their followers, a man standing outside in the roasting sun, said only that he was awaiting orders from Ahmad al-Qubaisy, a conservative religious sheik based in Baghdad.

"He is telling us not to hit the Americans right now," said the man, who did not want to give his name. "But we are ready to push them out of our town in an instant."

Children curse

On the lumpy street behind him, patrolling Humvees zipped by, the U.S. soldiers inside waving at curse-hurling children.

Even as Iraqi guerrillas chucked grenades at the office of Fallujah´s U.S.-appointed mayor, Army engineers were pouring $100,000 worth of repairs into the town´s dilapidated power lines, water mains and schools.

"We´re all competing, so to speak, for the loyalties of the people of Fallujah," said Watson, the intelligence officer. "They´ve got to choose between the Sunni clerics and a Western-type democracy." (Copyright © 2003, Chicago Tribune 06/18/03)