Iraqi, U.S. forces battle al-Sadr's militia
U.S. State Department vows 'no concessions to terrorists'
U.S. Marines aid Iraqi security forces against a local militia in Najaf.
Insurgents and Iraq's new regime vie for public opinion.
Four Jordanians kidnapped in Iraq return home.
BAGHDAD, Iraq (CNN) -- U.S. military forces on Thursday joined Iraqi security forces fighting the militia loyal to radical Shiite cleric Muqtada al-Sadr in the holy city of Najaf, according to Iraqi and U.S. military officials.
U.S. forces, responding to a request from the Najaf governor's office, began fighting alongside the Iraqi forces at 11 a.m.
Eleven deaths were reported -- 10 Iraqis and one U.S. soldier.
A member of the U.S. 13th Corps Support Command was killed and five others were wounded when a convoy was attacked with a rocket-propelled grenade and small-arms fire near Najaf, the U.S. military said.
With the death, 923 U.S. troops have died in Iraq since the start of the war, including 686 under hostile circumstances.
Among the 10 Iraqis killed was an Iraqi police officer. A spokesman for al-Sadr said six of the 10 were members of the Mehdi Army -- al-Sadr's militia.
Al-Hakim hospital reported that two Iraqi civilians died. Iraq's Health Ministry said a worker at Najaf's general hospital was killed when it was hit by mortar fire.
A U.S. helicopter carrying a wounded American service member was shot down by small-arms fire, a senior coalition official said. Two more U.S. military personnel were injured.
Iraqi police, members of the Iraqi Civil Defense Corps and U.S. Marines were battling the insurgents, the Najaf governor's office said.
At one point, the Marines called in close air support, and a plane dropped a 500-pound bomb on a suspected mortar position.
The clashes went on in the city center, about 1,000 yards (meters) from the Imam Ali mosque in the Old Town section, according to the Iraqi Defense Ministry and the governor's office. Najaf is about 80 miles (130 kilometers) south of Baghdad.
Announcements through the loudspeakers at the mosque claimed the shrine had been damaged by the U.S. military and called on the people of Najaf to fight back. Najaf has a population of 560,000, according to GlobalSecurity.org.
Asked about the mosque being hit by U.S. or Iraqi forces, a coalition forces spokesman said he would be "very suspect of that accusation."
A U.S. Marine quick reaction force was deployed in Najaf earlier in the day as the city's main police station came under fire twice within two hours, a U.S. military statement said.
The Marines joined Iraqi security forces in defending the police station but fired no shots as Mehdi Army members withdrew, the statement said. No Marines were hurt, and the number of Iraqi casualties was not immediately known.
"A significant number of aggressors, presumed to be members of the self-designated [Mehdi] Army, began attacking the station with heavy machine guns, RPGs, mortars, and small arms around 3 a.m.," the statement said.
"This came after an initial attack on the police station around 1 a.m. was unsuccessful."
On Wednesday, the Mehdi Army released five of six Iraqi police officers kidnapped Sunday. A spokesman for the Najaf governor's office said all five were returned with an "X" branded on their backs using a metal bar.
"We consider this to be an unacceptable act of terrorism," the governor's office spokesman said.
The hostages were taken because one of the leading sheikhs of the Mehdi Army was arrested by Karbala police, sources from the Najaf governor's office said Tuesday.
Elsewhere Thursday morning, a suicide car bomber killed six people and wounded 24 others near an Iraqi police station south of Baghdad, according to Iraq's Ministries of Health and Interior.
The bomber drove a mini-bus near the station in Mahawil, about 40 miles (64 kilometers) south of the Iraqi capital, according to Interior Ministry official Col. Adnan Abdul Rahman.
British troops fight in Basra
British coalition troops fought two gunbattles with Shiite militiamen in the southern city of Basra on Thursday, a spokeswoman from the British Ministry of Defense said.
The troops were "engaged by small-arms fire" in Basra's city center and one militia member was killed in each battle, she said. No coalition casualties or damage was reported.
'No concessions to terrorists'
Responding to the ongoing rash of kidnappings and slayings in Iraq, the U.S. State Department announced Wednesday a new policy statement on terrorism -- vowing that "no concessions" will be made.
"As members of the multinational force in Iraq operating under U.N. Security Council Resolution 1546, we're united in our resolve to make no concessions to terrorists, nor to succumb to terrorist threats," said State Department spokesman Richard Boucher.
"We understand that conceding to terrorists will only endanger all members of the multinational force, as well as other countries who are contributing to Iraqi reconstruction and humanitarian assistance." (Full story)
CNN's Tomas Etzler, Kevin Flower, Andrea Koppel, Eden Pontz, Kianne Sadeq and Mohammed Shareef contributed to this report.