Between three and six American soldiers are killed and another 40 wounded every week in Iraq by an enemy that has become more lethal and sophisticated since the fall of Baghdad (searchin April, the commander of coalition forces said Thursday.

Nearly six months after the fall of Baghdad, U.S. soldiers are still facing 15-20 attacks a day, including roadside bombs, Lt. Gen. Ricardo Sanchez (searchsaid. Seven to 10 attacks a day involve small groups of fighters.

"They're getting attacked every day," Sanchez said of his soldiers. "I'm having soldiers wounded at a rate of about 40 a week and getting killed anywhere from three to six soldiers a week."

Most attacks occur in Baghdad and the surrounding Sunni Muslim stronghold to the west and north of the capital, although it's unclear whether Iraqi or foreign forces account for the majority.

"The enemy has evolved -- a little bit more lethal, a little more complex, a little more sophisticated, and in some cases, a little bit more tenacious," Sanchez said.

Since May 1, when President Bush (searchdeclared the end of major combat operations, 90 American soldiers have been killed by hostile fire in a low-level, guerrilla-style insurgency. A total of 317 Americans have died since the war began March 20, according to the Pentagon.

On Wednesday alone, three Americans were killed: a soldier from the 1st Armored Division who was shot while on patrol in the al-Mansour district of Baghdad; a female soldier from the 4th Infantry Division who died when a roadside bomb exploded about 300 yards from the main U.S. base in Tikrit, Saddam's hometown; and another soldier from the 4th ID, who died after a rocket-propelled grenade attack on a convoy near Samara, 60 miles north of the Iraqi capital.

While most wounded Americans are treated at two military hospitals in Iraq, those with more serious injuries are evacuated to the U.S. military hospital in Landstuhl, Germany.

Landstuhl has been receiving an average of 40 to 44 patients a day from Iraq, but only about 10 to 12 percent are classified as "battle injuries," said hospital spokeswoman Marie Shaw.

Since the start of the war, the hospital has treated 6,684 patients -- 5,377 after May 1, she said.

"What we don't see a lot of, though we see some, is gunshot wounds," Shaw said. "We see a lot of shrapnel wounds, some amputations, some burns -- mostly from individual explosive devices."

Sanchez blamed the increasingly sophisticated resistance on the addition of foreign fighters entering Iraq from Syria and northern Iran.

"We believe there is in fact a foreign fighter element. There is a terrorist element focused on the coalition and international community in general and the Iraqi people to try to disrupt the progress being made," Sanchez said.

Coalition officials are not discounting the possibility that Saddam Hussein may have a hand in coordinating the violence, he said.

"It's very clear there is local command and control. We still are not seeing the national command and control structure," though there are some signs of regional coordination, Sanchez said.

In Thursday's violence, about 10 U.S. soldiers came under fire in Fallujah, 30 miles west of Baghdad, in front of the mayor's office. No Americans were hurt but one Iraqi bystander was killed and four people, including a mother and her 4-year-old daughter, were wounded, hospital officials said.

Shortly before the attack in Fallujah, a fuel tanker in a U.S. convoy near Amiriyah, southeast of the city, was hit by a mine or roadside bomb, according to Mohammed Hamid, who lives nearby. He said a soldier in the passenger seat of the cab pulling the tanker was killed and the driver was wounded. The military had no information on that attack.

In nearby Khaldiyah, a roadside bomb exploded as a U.S. convoy was passing, but did not damage the American vehicles. Elsewhere, a soldier from the 101st Airborne Division and an Iraqi bystander were wounded in an ambush in Mosul, U.S. officials and Iraqi police said.

Meanwhile, U.S. officials said soldiers from the 101st Airborne Division raided three weapons caches in the Mosul area this week, seizing 15 surface-to-air missiles, 300 rocket-propelled grenades, 10 grenade launchers, 8,000 rounds of machine gun ammunition, rifles, mortar shells and two crates of plastic explosives.

The raids took place Tuesday, On the same day, Iraqi police raided a mosque in Mosul and confiscated two machine guns, 267 mortar shells and hundreds of rounds of ammunition, according to U.S. officials.

Iraqi officials have been urging the coalition to transfer security responsibility to Iraqis, echoing calls by France, Germany, Russia and other major countries who want to see a quick restoration of Iraqi sovereignty. On Thursday, a member of the U.S.-appointed Iraqi Governing Council, Abdel-Aziz al-Hakim, urged the United States and Britain to "change their wrong policies and put security matters in the hands of Iraqis."

The U.N. Security Council debated a new U.S. draft resolution on handing over power to Iraqis and giving the United Nations a larger role. But the new measure did not set a timetable for the Americans and British to cede power -- a key demand of France, which has called for sovereignty to be transferred by the end of the year.

However, Secretary of State Colin Powell said a hasty transition to civilian rule could produce a "failed state." Powell insisted that "we want Iraqis to be in the driver's seat" although the process of fostering democracy in Iraq takes time. The pace should be determined by the Iraqis themselves, he said.

Sanchez, the commanding general, said U.S. coalition officials are working on training an Iraqi police and military force but it will take time before it can take full responsibility for Iraq's security.