U.S. forces and insurgents fought a pitched battle Thursday in a central neighborhood of Baghdad, where at least nine Bradley Fighting Vehicles poured cannon fire into a downtown apartment building that had been seized by guerrillas.

Iraqi officials said after the clash that they had captured a leader and 25 members of a gang responsible for attacks in the city.

The fight was one of several clashes in Baghdad, which is taking on the pall of a besieged city despite assurances by government officials that their forces remain in control. Long lines of automobiles waited for fuel at the few gas stations still open for business. Mosques closed, markets were empty, businesses shut down early. Women and children stayed indoors, and men did not venture out far.

Baghdad's Sadr City, a Shiite Muslim slum of about 2 million, remained virtually encircled by U.S. troops and Iraqi forces. The area remained largely under the control of supporters of the Shiite cleric Moqtada Sadr, who was under siege 90 miles to the south in Najaf. Iraqi officials said they had defused 300 explosive devices around Sadr City's perimeter.

The area was unusually quiet Thursday evening. A resident of Sadr City said by telephone that members of the Mahdi Army, the Shiite militia loyal to Sadr, were in front of television sets.

"Now everyone in Sadr City is busy watching the soccer game," said the resident, who would not give his name. "Everybody is celebrating that the Iraqi team won." Playing in the Olympic Games in Greece, Iraq upset Portugal, 4-2.

The heaviest fighting in Baghdad erupted early in the day in the downtown area of Haifa Street. U.S. forces took the lead, while the lightly armed Iraqi police stayed in the rear.

Iraqi Defense Minister Hazim Shalan said the clashes culminated when the Iraqi National Guard "carried out an attack on some safe houses taken over by former Baathists and other terrorists" on Haifa Street. "We were able to arrest the leader of a dangerous group, who has been wanted for a year. Others of his group were arrested."

Bradley Fighting Vehicles roared into the battle, guns and cannons blazing, and F-15 jets dropped flares and flew low, but apparently did not drop any bombs. Attack helicopters buzzed about an apartment building, while armored vehicles fired toward it from the other side of Haifa Street. A crackle of automatic weapons fire answered.

As the fighting subsided, billows of black smoke rose to smudge the bleached sky just as the call to afternoon prayers floated out from a nearby mosque.

Lt. Col. Heider Abdul Rasul, a commander of the Iraqi National Guard, said insurgents used automatic weapons and grenades during the fight. But "we now have the leader in our prison, along with 25 of his men," Rasul said.

He said he had no information on casualties. Officials at a local hospital said they had not taken in any casualties because the area was still under military control and the injured could not be moved.

A spokesman for the U.S. Army's 1st Cavalry Division said Thursday night that because the operation was continuing, he could not give any details of the fighting.

Elsewhere in Iraq, two U.S. Marines were killed and three were injured when a CH-53 helicopter crashed late Wednesday in volatile Anbar province. No enemy fire was observed at the time of the crash, the military said. The military declined to say where the crash occurred in the large western province.

Also Wednesday night, gunmen in Mosul killed two police officers and two bystanders, according to Iraqi police.