Insurgent attacks spread Monday to another Sunni Muslim city, Baqubah, and a nearby village, where bands of armed men attacked two police stations simultaneously, the U.S. military said. American forces used airstrikes to blunt the assault, the latest that insurgents have launched in apparent response to the U.S. offensive in Fallujah.

Two 500-pound bombs were dropped on insurgent positions after a two-hour firefight in which guerrilla reinforcements arrived by bus, took positions on a roof and blocked a road, according to the U.S. military.

Meanwhile, fighting continued in Mosul, a city of 1.8 million, where large numbers of insurgents went on the offensive late last week. "I expect the next few days will bring some hard fighting," said Brig. Gen. Carter Ham, the senior U.S. commander in the area. "The situation in Mosul is tense but not desperate."

U.S. forces last week stormed into Fallujah, which insurgents had controlled since spring. American policymakers portrayed the operation as a decisive move to clean out a major stronghold of foreign fighters and Iraqis opposed to the country's interim government.

The insurgents have struck back hard in Fallujah and also turned up the heat in many other cities dominated by Sunni Muslims, who were favored over the majority Shiite Muslims by the government of former president Saddam Hussein. Operating in unusually large groups, fighters have attacked in Ramadi, to the west of Fallujah, and Samarra, Baiji, Tall Afar, Hawija and Mosul to the north.

Their strategy was stated Monday in a new recording attributed to Abu Musab Zarqawi, the Jordanian leader of a large insurgent group affiliated with al Qaeda. If the U.S. military "finishes Fallujah, it will move in your direction," the voice said to be Zarqawi's warned followers. "Beware and deny it the chance to carry out this plan."

The speaker said that U.S. forces were overextended and would be unable to respond everywhere. "Shower them with rockets and mortars and cut all the supply routes," he said.

A senior Iraqi official said Monday that about half of Mosul's police officers have returned to duty, reinforced by an armored U.S. battalion and truckloads of Iraqi troops and police commandos. But sporadic fighting continued in the city, and insurgents set on fire an oil storage facility outside the city.

Interior Minister Falah Naqib grew emotional during a news conference in Baghdad while describing the killing of a Mosul police officer. "Yesterday in Mosul, they abducted a wounded member of the police from the hospital," Naqib said. "They dismembered him.

"He was wounded," he repeated. "They dismembered him, and then his remains were hanged in a public square until his fellow policemen were able to secure his body.

Close to 1,000 members of the interim government's security forces have died in the insurgency. Intimidation of those who remain is a prime goal of the guerrillas. Naqib said that threats are directed not at recruits but at their family members. Kidnappings of recruits are also on the rise.

Meanwhile, the office of interim Prime Minister Ayad Allawi confirmed reports that two female relatives of Allawi's had been released by kidnappers but that Allawi's elderly male cousin remains captive.

The badly mutilated body of a Western woman, assumed to be another kidnapping victim, remained unidentified after being found on a Fallujah street.

To the east, new fighting in Baqubah, long a flash point for attacks on U.S. forces, began about 7 a.m. with simultaneous attacks on two police stations, one in the city, the other in the nearby village of Buhriz.

Protected by dirt-filled fences to guard against car bombs, the stations were targeted by rocket-propelled grenades, rifle fire and, at one station, fire from a heavy machine gun, according to Army Capt. Bill Coppernoll, a spokesman for the 1st Infantry Division.

Elements of the division responded and reported taking fire from multiple spots, including a mosque. A search of the area around the mosque produced three rocket-propelled grenade launchers, 29 grenades, two mortar tubes, 10 mortar rounds and hundreds of rounds of ammunition for AK-47s assault rifles, the military said in a statement.

Four American soldiers were wounded in the fighting. The military reported that more than 20 insurgents were killed, and news services said seven civilians and five police officers, including the police chief of Buhriz, also died.

In a separate attack in Baghdad, seven civilians were killed and seven wounded when a mortar round landed in the Dora neighborhood. At least five suicide car bombers wounded at least nine U.S. troops elsewhere in Iraq, the Associated Press reported.

Iraqi insurgents run from a burning oil facility near Mosul. Gunmen set fire to the station, where oil is stored and then pumped to the Ceyhan port in Turkey.