The bodies of what were believed to be nine members of the Iraqi National Guard fighting anti-US forces have been found in the northern city of Mosul on Saturday.
The men, discovered in an industrial area not far from the scene of some of the worst clashes in Mosul, appeared to have been executed, as they all had a bullet in the head and their bodies were also badly burned.
Senior Iraqi and US military sources said the dead troops probably belonged to an Iraqi army unit that had joined American forces for a massive onslaught against fighters in the country's third-largest city.
"These are not my men. They all have IDs from outside Baghdad. It seems they had been on leave and were returning to their barracks," said Iraqi national guard Lieutenant Colonel Ammar Abd al-Hadi.
"Some of the guys from an army unit recently moved to one of the US bases to take part in the operation. They have some guys missing," said Lieutenant Colonel Michael Kurilla of the 1st Battalion 24th Regiment of the Stryker Brigade.
A witness said he saw gunmen execute some of the men who were found dead.
"A group of five young men pulled up in front of the nearby veterinarian hospital, shot four men and dumped the bodies on the railway tracks," said Abu Abid.
Iraqi and US forces have killed 15 anti-US fighters and arrested 45 other suspected fighters over a 24-hour period in Mosul that included a dusk raid on Friday on a mosque and tea house in the northern city's old quarter, US military officials said.
Armed fighters destroyed voter
registration forms in a warehouse
But the city's fighters appear to be hitting back at soft targets with the US military saying it received unconfirmed reports that 12 members of the Iraq's paramilitary national guard had been kidnapped and possibly executed.
The fighters also destroyed an interim government-owned warehouse on the west side of the city, where voter registration forms for the January elections were turned into smouldering ashes, according to an AFP reporter embedded with the US military.
A force of about 400 newly trained Iraqi commandos descended in pick-up trucks on the city's historic centre shortly after evening prayers.
Mosques have been raided in
Mosul, Falluja and Baghdad
Their commander, Major General Rashid Flaih, and US military officials said the target was a meeting place for anti-US leaders.
Commandos wearing dark-green military fatigues and ski masks flashed lights at shuttered shops and crumbling buildings and fired warning shots into the air as they strutted down deserted streets, witnesses said.
A dozen US soldiers on foot observed from a distance while others waited in armoured Stryker vehicles on the edge of the neighbourhood in case the commandos needed reinforcement, while two US helicopters provided air support.
Flares fired by a US warplane lit up the sky.
The commandos entered a mosque on a side street and detained a number of people. They also rounded people up in a nearby tea house who appeared to be unarmed and were playing dominoes and cards when the troops arrived.
A grocery shop owner was also among those arrested.
A US military official confirmed that 23 suspects in total were held.
Earlier, US commanders said up to 100 "insurgents" were thought to be in the neighbourhood, among them leaders, and that the aim of the operation was to draw them out into the open.
"We are finding the (insurgent) pockets with Iraqis, and going and asking them to come out and fight," said Colonel Robert Brown, a senior US military commander in Mosul.
He said 15 had been killed in joint operations throughout the city over the past 24 hours.