U.S. Army soldiers fire a 21-gun salute during a memorial at Al Asad air base November 6, 2003 for the 15 victims of the shooting down of the Chinook helicopter in Iraq last weekend. Against a backdrop of 15 helmets resting on M-16 rifles, American soldiers honored their comrades, victims of the single deadliest incident for U.S. forces since they invaded Iraq.  [Reuters]

In retaliation, American troops backed by Bradley fighting vehicles swept through Iraqi neighborhoods before dawn Saturday, blasting houses suspected of being insurgent hideouts with machine guns and heavy weapons fire.

"This is to remind the town that we have teeth and claws and we will use them," said Lt. Col. Steven Russell, commander of the 1st Battalion, 22nd Infantry Regiment.

Russell also said the 11 p.m. to 4 a.m. curfew, which had been lifted at the Oct. 27 start in Iraq of the Islamic holy month of Ramadan, was reinstated Friday night.

The U.S. death toll for the week climbed to 32, including those aboard the Black Hawk. Two other soldiers were killed near Mosul, raising concerns that the insurgency was spreading north.

U.S. policy, meanwhile, suffered another setback as Turkey decided not to send troops to Iraq because of strong opposition from Iraqi officials.

The Black Hawk crashed on an island in the Tigris River and burst into flames — the third crash caused by hostile fire in two weeks and the second causing fatalities. Maj. Josslyn Aberle said the cause of the crash had not been determined, but several other officers believed it was shot down.

"We believe it was something fired from the ground from the side of the river," Russell said. "We believe it was brought down by gunfire."

After the raids before dawn Saturday, intermittent explosions and the crackle of random gunfire could be heard across Tikrit.

The helicopter, assigned to the 101st Airborne Division, went down about 9:40 a.m. about a half mile from the U.S. base in Saddam Hussein's former palace, which serves as headquarters for the 4th Infantry Division.

Afterward, attack helicopters cruised throughout the day over Saddam's hometown, swooping low over villages and farms as rescuers picked through the charred wreckage of the aircraft.

Late Friday, U.S. troops fired mortars and a U.S. jets dropped at least three 500-pound bombs around the crash site, rattling windows over a wide area in an apparent show of force. Other U.S. jets streaked over Tikrit after sundown. At least three mortars were also fired onto the U.S. compound but caused no damage.

The dead included the Black Hawk's four-member crew and two soldiers from Department of the Army headquarters, according to a Pentagon spokesman, Maj. Steve Stover.

In Mosul, 250 miles north of Baghdad, guerrillas attacked a convoy with rocket-propelled grenades and small-arms fire Friday. The military said one U.S. soldier died and six others were wounded in the clash. Another soldier died in Mosul the night before when a homemade bomb exploded, the military said Friday.

Both of those soldiers, as well as the Black Hawk's four-man crew, were from the 101st Airborne Division, based at Fort Campbell, Ky.

Three others were injured later Friday when a roadside bomb exploded near the Mosul Hotel, which is now used as a military barracks, the military said. Mosul, Iraq's third largest city, had been considered relatively safe for American soldiers until an escalation of attacks there over the past three weeks.

U.S. officers have long been concerned about the safety of aviation because of the hundreds, perhaps thousands, of shoulder-fired missiles still missing in Iraq after the collapse of Saddam's regime in April.

On Oct. 25, insurgents shot down a Black Hawk over Tikrit, injuring one crewman. On Sunday, insurgent gunners brought down a Chinook transport helicopter west of Baghdad, killing 16 Americans in the bloodiest single strike against U.S. forces since the war began March 20.

An Apache attack helicopter was shot down in June in the western desert but the two crew members escaped injury.

The latest fatalities brought to 32 the number of American soldiers who have died in Iraq in the first week of November. That includes one 1st Armored Division soldier who died in a non-hostile shooting incident.

In addition, two American civilian contractors working for the U.S. Army Corps of Engineers and a Polish officer also died in attacks in the past seven days.

The death toll of 32 was by far the largest for any seven-day period since President Bush declared an end to hostilities on May 1 — mainly due to the Chinook crash Nov. 2 that killed 16. In all of October, for instance, there were 42 deaths; in all of September, were 31.

The U.S. military said that the number of daily attacks on coalition forces dropped to 29 last week from a spike of 37 the week before but cautioned against drawing conclusions from the decrease.

U.S. officials had hoped to encourage more countries to send troops to Iraq to relieve the burden on American forces. Turkey's parliament agreed last month to allow the government to send Turkish troops, a move which drew sharp opposition from Iraqi politicians.

But Secretary of State Colin Powell and Turkey's foreign minister have agreed that Turkey will not send peacekeeping troops to Iraq, officials said Friday, after plans for a deployment raised sharp opposition from Iraqis.

The decision reverses what had been a significant victory for Washington, which has pressed hard for Turkey to join peacekeeping efforts in its neighbor to the southeast to help U.S. troops there. Turkey is the only majority Muslim nation in NATO.

Powell and Foreign Minister Abdullah Gul spoke Thursday night by telephone and agreed that the offer of Turkish troops would be withdrawn, State Department spokesman Richard Boucher said.

In Baghdad, about 500 Sunni Muslims marched Friday to coalition headquarters to demand the release of 36 clerics arrested in recent months. Protesters chanted Islamic slogans including "America's army will be wiped out," and "America is the enemy of God." They also carried a banner reading "Prisons ... will never terrify us."

Marchers stopped at the heavily fortified compound and sent a three-member delegation inside to present their demand. After a 45-minute meeting, the three delegates returned, saying they has been promised "that something good would happen," according to one of them, Sheik Awad al-Haradan.

Another delegate said the Americans asked them to work on stopping anti-coalition attacks in Iraq.

"They wanted us to give them guarantees that what they call violence ends. We told them that this will only end when the last American soldier leaves the country," said Sheik Abdel-Sattar al-Janabi.