Baghdad, Iraq ? Insurgents killed 19 Iraqi security forces Saturday in clashes around Baqouba, while U.S. and Iraqi forces intensified an offensive in a city that the Americans subdued last year – only to have the Iraqis lose control.

Eight policemen died in a pair of shootouts in Baqouba, 35 miles northeast of Baghdad, officials said. Six policemen and two soldiers were killed in another gunbattle in Buhriz, a suburb of the Baqouba, officials said.

Three Iraqi soldiers also died Saturday when their convoy was attacked by gunmen near Adhaim, 30 miles north of Baqouba, police said.

To the north, fighting raged for a second day Saturday in the outskirts of Tal Afar, an ethnically mixed insurgent stronghold.

U.S. and Iraqi officials urged civilians to leave affected areas of the city, 260 miles northwest of Baghdad, a sign that the Americans were preparing a major assault. U.S. forces crushed insurgents in Tal Afar last fall, leaving only about 500 American soldiers behind and handing over control to the Iraqis.

But Iraqi authorities lost control of the city, and insurgent ranks swelled. That forced the U.S. command to shift the 3rd Armored Cavalry Regiment from the Baghdad area to Tal Afar to restore order.

On Saturday, U.S. and Iraqi forces were firing at insurgents on the western side of the city, Iraqi officials said. Elsewhere, American and Iraqi forces were moving from house-to-house, searching for weapons and arresting men capable of firing them, Iraqi authorities said.

Hospital officials said they were unsure of casualties because it was too dangerous for ambulances to reach the area. Officials said they hoped to get ambulances into the area today.

U.S. and Iraqi officials had hoped that a new constitution, finalized Aug. 28 after weeks of intense negotiations, would help bring Iraq’s factions together and in time lure Sunni Arabs away from the Sunni-dominated insurgency.

Instead, the bitter talks sharpened communal tensions at a time when Sunnis and Shiites accused extremists from the other community of killing their civilians. Discreet talks are under way to make changes in the language of the draft to ease Sunni Arab hostility to the document.

However, both Sunni and Shiite community leaders are gearing up for a decisive political battle in the Oct. 15 referendum. Sunni clerics are urging their followers to reject the charter while most of the Shiite clergy supports it.

Hundreds of Sunni Arabs met in Baghdad on Saturday to urge the defeat of the constitution, which threatens “Iraq’s division.”

The leader of the biggest Shiite party, the Supreme Council for the Islamic Revolution in Iraq, said Saturday there was a “conspiracy to annihilate the Shiite sect in Iraq.”

Party leader Abdul-Aziz al-Hakim spoke at a funeral for some of the nearly 1,000 Shiites killed in the stampede that broke out Thursday during a Shiite procession at a Baghdad bridge. The stampede began because of rumors that a suicide bomber was among the crowd.