Coalition troop losses continued to mount, with one US soldier killed in a roadside bombing in Baghdad Saturday and two marines dead in a similar attack west of the capital, the US military said.

The deaths brought to 12 the number of US servicemen killed in Iraq since Tuesday and to 1,684 the overall toll since the March 2003 invasion, according to AFP tallies based on Pentagon figures.

In the countryside just to the south, dubbed the Triangle of Death for its insurgent violence, 11 Iraqi construction workers were killed when gunmen attacked their minibus, police said.

Eleven people died when a blast tore through Baghdad's mainly Shia Shula district, shortly before a night-time curfew came into effect and as US and Iraqi officials warned against complacency despite counter-insurgency successes.

An eight-months pregnant woman, her unborn child and husband were among the dead.

In the second blast, three Wolf Brigade commandos were killed when a suicide bomber disguised as a commando walked into their central Baghdad barracks.

And in the latest attack, four Iraqis were wounded when a suicide bomber blew up an empty fuel tanker near the Slovak embassy in the capital's central Jadriyah neighbourhood, an interior ministry official said.

The embassy could not be reached for comment.

Interior Minister Baqer Jabr Solagh told journalists that eight people had been detained in connection with the Shula blast.

He said the commando strike had been carried out by a former brigade member and that the force's chief Major General Mohammed al-Quraishi was the target.

"The terrorists will try to penetrate the security cordon that we have erected around Baghdad and they succeeded in doing that at a late hour on Friday night in Shula," he said.

A doctor said his hospital had received 21 wounded commandos following the strike against the vanguard of those trying to bring peace to the capital.

A patriotic song regularly broadcast on Iraqi television says that members of the fearless brigade "disarm bombs with their teeth".

The commando unit had come to the capital from the main northern city of Mosul as part of Operation Lightning, a major offensive launched amid fanfare in May and reportedly involving 40,000 Iraqis forces.

Solagh said that 1,380 "terrorists" and 219 "suspected terrorists" had been detained in the sweep, including 11 non-Iraqi Arabs, and 27 car bombs primed for use had been defused.

Another 36 "terrorists" had been killed, along with 37 civilians and four security personnel.

Asked how the confirmed "terrorists" had been identified, the minister said: "If we find in their possession hand grenades, certain tapes and medium-calibre weapons, then that tells us they are terrorists. Plus intelligence."

He said 73 of the "suspected terrorists" had since been released.

The minister praised the operation's success and promised it would soon be extended outside Baghdad, without saying when or where.

"Car bombs have gone down from 12 to 0.6 a day," he said pointing to a bar graph on a screen.

The Shia-led government of Ibrahim al-Jaafari is eager to demonstrate that it is able to control the security situation and often points to mistakes committed under the US-installed interim government of Iyad Allawi which had a Sunni Arab as interior minister.

Even before the fresh blasts, a US commander had warned of the likelihood of renewed violence.

"The enemy is pretty frustrated and looking for the opportunity to have large-scale coordinated attacks. That could happen within the week, but it won't last weeks or even days," he said, because "they don't have public support."

The bullet-riddled corpses of two brothers and a cousin were found on a main road in south Baghdad, after they were lured from their homes by men in police uniforms the night before, an interior ministry official said.

Three police commandos were killed in a drive-by shooting, while a US patrol killed two insurgents after they also came under fire from a passing car.

The US commander had warned that insurgents would resort to more such shootings as it became more difficult for them to get car bombs to their intended targets.

The same tactic was used in Saturday's attack south of Baghdad in which the 11 builders were killed.

"Eleven Iraqis were killed and three others wounded when men aboard two cars opened fire on a minibus taking construction workers from Jbala, 70km south of Baghdad, to the capital," said Captain Said al-Kraimi.

PM Jaafari said Thursday that Operation Lightning would be extended to other cities and justified it by the "exceptional circumstances" facing the country.

Almost 700 people died in a frenzy of car bombings and other attacks in May, one of the bloodiest months since the US-led invasion in March 2003.