(Adds details on Mosul killings)

By Dean Yates and Ibon Villelabeitia

BAGHDAD, April 22 (Reuters) - Car bombs killed 18 people in Baghdad on Sunday and gunmen shot dead 23 workers from a minority sect after pulling them off a minibus in Iraq's northern city of Mosul in an apparent revenge attack.

South of Baghdad, the U.S. military said it carried out air strikes on a known al Qaeda meeting location, killing 15 militants. Ground forces later killed another three militants in the operation, the military said in a statement.

Among the attacks in Baghdad, two suicide car bombers rammed their vehicles into a police station in a mostly Shi'ite neighbourhood, killing 12 people and wounding 95, police said.

It was one of the deadliest bombings aimed at Iraq's security forces since a U.S.-backed security crackdown was launched in Baghdad two months ago in a last ditch attempt to halt all-out sectarian civil war.

Most of the dead were civilians, police said. The blasts damaged the police station and also largely destroyed a garage next door, collapsing rubble onto a dozen cars.

"Look at the situation Iraqis are living in. You see blasts whenever you try to go out to earn a living," said one witness.

In a separate attack, a car bomb in a Shi'ite enclave in the mostly Sunni neighbourhood of Saidiya in southern Baghdad killed six civilians and wounded 37 people, police said.

In Mosul, gunmen killed 23 textile workers from the minority Yazidi sect after forcing them out of a minibus.

Brigadier-General Mohammed al-Waggaa said the gunmen stopped the vehicle and gunned down the workers. A source at a local hospital said the 23 were killed.

Waggaa said the mass killing appeared to be in retaliation for an incident in which a Yazidi woman was stoned to death several weeks ago for converting to Islam. Another police source who declined to be named confirmed the incident.

Yazidis are members of an ancient minority sect and live in northern Iraq and Syria.

TROOPS TO STAY

U.S. and Iraqi forces have poured thousands of extra troops into Baghdad over the past two months.

While the boost in troop levels has reduced killings by sectarian death squads, car bomb attacks still plague the city. A wave of car bombs killed nearly 200 people last Wednesday.

U.S. Defense Secretary Robert Gates told Iraq's leaders on Friday that progress in reconciling warring Shi'ites and Sunni Arabs would be an "important element" when Washington decides this summer whether to maintain the higher troop numbers.

But remarks by senior U.S. commanders and officials and a change in Army deployment plans suggest the higher level of American troops will likely remain for months beyond the summer.

The Bush administration has avoided predicting how long it will keep the beefed-up force of about 160,000 troops ordered by the president in January.

It has said only that it will review progress in the late summer. The implication is that troops could then start to be withdrawn but that appears improbable.

The U.S. military commander in Iraq, General David Petraeus, said during Gates' visit that the buildup of some 28,000 extra U.S. troops would not even be complete for another two months.

President George W. Bush's Republican administration is under unrelenting pressure from Democrats, who won control of Congress last November largely due to voter anger over the war and believe they have a mandate to push for withdrawal.

Any suggestion the buildup may last until the year's end or beyond risks fuelling domestic opposition to the war. (Additional reporting by Yara Bayoumy, Wissam Mohammed and Ahmed Rasheed, and Andrew Gray in Washington)

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