FALLUJAH, Iraq, September 13 (IslamOnline.net & News Agencies) - Heavy gunfire crackled through the city of Fallujah on Saturday, September 13, as scores of heavily-armed tribesmen vowed revenge against U.S. troops involved in a "friendly fire" incident that killed nine Iraqi security personnel as the U.S. military apologized for the "unfortunate incident".

A chorus of Kalashnikovs reverberated around the city as the bodies of the dead were brought to the Hamad al-Mahmud Mosque, opposite police headquarters, an Agence France-Presse (AFP) correspondent said.

Mourners who gathered under tribal banners vowed to avenge their lost love ones.

"We will keep your blood warm with the blood of the American killers," they chanted. Many wore masks and carried rocket-propelled grenade (RPG) launchers.

An appeal over the mosque loudspeaker to stop firing in order to avoid accidental casualties brought a brief respite.

Two suspected thieves and a Jordanian official were also killed in the shooting that left another nine wounded in the city where simmering friction against occupying U.S. troops has resulted in a recent upsurge in violence.

Thousands were pouring into the center of Fallujah after calls from tribal elders for a local show of force in the wake of Friday's shootings which has put this city on a knife's edge.

Three days of mourning has been declared and a "major" strike called.

No U.S. forces were in sight as the first coffin arrived at the Mosque amid hails of gunfire shot in the air from Kalashnikovs with tribal sheikhs and Bedouin tribesmen in black cloaks and white flowing robes paying their respects.

District patrol chief Lieutenant Colonel Jalal Sabri paid tribute to the independence of his forces and their success in catching criminals.

"We've always been independent because this a tribal area and ours is a very religious town," he said of the city which sits in the middle of a Sunni Muslim tribal belt, 50 kilometers (30 miles) west of Baghdad.

"That's why our patrols are independent and we've had major successes in our work capturing criminal gangs and infiltrators from outside, including bandits from foreign countries like Egypt and Iran."

Asked whether an agreement had been reached to keep U.S. forces out of the area while the mourning ceremonies were underway, he said: "This is what we wished for, this is what we wanted from the beginning from them in Fallujah."

Enraged residents said they did not want the Fallujah mayor involved in the ceremony because his office was a symbol of the U.S. occupation of Iraq.

Meanwhile, the U.S. military apologized earlier Saturday for the shootings.

"The senior military leadership of the coalition has been in contact with the Jordanian military and Iraqi authorities to express our deep regrets and apologies," the army said in a statement read by Lieutenant Colonel George Krivo.

"We wish to express our deep regrets for this incident to the families who have lost loved ones," said Krivo, the coalition's chief military spokesman. He said an investigation had been launched.

Krivo said a U.S. patrol operating near the Jordanian hospital became embroiled in a three-hour firefight with "unknown forces" in the flashpoint Sunni town 50 kilometers (30 miles) west of Baghdad.

"Regrettably during the incident, extensive damage was done to the hospital and security personnel were killed, including eight Iraqis and one Jordanian national," his statement said.

Krivo said the investigation would be led by Brigadier General Jeffrey Schloesser, a personal representative of Lieutenant General Ricardo Sanchez, the commander of coalition ground forces in Iraq.

Schloesser is not in the chain of command of the unit involved, Krivo said. "He will be a disinterested and objective investigator."

Krivo would not say how long the query would take, but added: "We will release the results of the investigation once it is concluded. As long as the investigation is ongoing we cannot comment."

The U.S. military waited more than a day before issuing an initial statement earlier Saturday on the "unfortunate incident".

"While conducting operations against enemy forces U.S. soldiers were involved in an unfortunate incident near Fallujah in which a Jordanian hospital was damaged and at least one death of friendly personnel resulted," that statement said.

"We deeply regret this incident and express our condolences to the family of the deceased," it added.

Shortly before the first casket was delivered to the Mosque, resident Majid Nasser Jassem al-Mahdidi said that "the Americans came by force, they have stayed by force and they will leave by force".

Mahdidi said the shootings highlighted how little regard the American troops had for the police in Fallujah because the dead men should have been easily recognized by the vehicles they were driving.

"The reason why they fired shots at the vehicles was because they want the police to fight the resistance, they won't do that, it's not their job, their job is to fight the criminals.

"That's why the Americans fired on our boys."

Fallujah has been the scene of repeated attacks on U.S. troops. This included at least three attacks on Friday.

Sabri added that aggressive U.S. action against the police in Fallujah would have a negative impact on relations with occupying forces.

"So now the police in Fallujah are having to fight a battle on two fronts, one against the criminals and one against the Americans and we just don't know who to fight.

"We just want to be left to fight the criminals ourselves, the Iraqi police was established in 1921 and we know who are the good guys and who are the bad guys," he said.

Meanwhile, six U.S. soldiers have been wounded following two separate attacks involving a hand grenade and an "improvised explosive device" (IED), a spokesman for U.S.-led occupation forces in Iraq said Saturday.

Two soldiers were wounded after a hand grenade attack on a U.S. base in the troubled city of Ramadi, 110 kilometers (66 miles) west of Baghdad, on Saturday, the spokesman said.