BAGHDAD, Iraq (CNN) -- The security convoy that on Tuesday fired on a car in Iraq's capital, killing two Iraqi women, was an Australian firm, Iraq's Interior Ministry said. The firm, Unity Resources Group, has offices in Dubai.
A U.S. State Department official said the company had been providing security for a nongovernmental organization called Research Triangle Institute International, which is a USAID-based subcontractor doing reconstruction work.
Michael Priddin, Unity Resources Group chief operating officer, said in a written statement that initial information indicated the car approached the security team "at speed" and "failed to stop despite an escalation of warnings which included hand signals and a signal fire."
"Finally, shots were fired at the vehicle and it stopped," he said. "Unity is now working with the Iraqi authorities to determine the outcome of this incident."
Iraqi Interior Ministry spokesman Brig. Gen. Abdul Kareem Khalaf said Unity's "four vehicles were driving from the outer Karrada area toward the National Theater in central Baghdad."
"They opened fire and killed two young Christian women who were in the car," he said. See map locating the incident »
He said the women, ages 30 and 32, were hit by 19 bullets.
Research Triangle Institute International spokesman Patrick Gibbons said "no RTI staff members were involved or present when the incident occurred."
"URG had completed their transportation mission [of RTI personnel] and were returning to their base of operations at the time of the incident," he said. Watch more about the car and the private security contractors »
URG, Khalaf said, apologized to the Interior Ministry and said it is committed to compensating the families of the two women and taking action against its employees, depending on what an investigation reveals.
The ministry and URG have launched investigations, he said. He added that URG is registered with the ministry and had no prior violations.
The incident came during a period of scrutiny over the activities of private security contractors such as Blackwater USA, which guards U.S. diplomats.
Iraqi government spokesman Ali Dabbagh called Tuesday's incident another example of excessive force being used against innocent Iraqis.
"They had excessive force to attack the women, and we feel this is part of the violation of some of the security companies which they are practicing against the Iraqis," he said.
"There is an anger in the Iraqi government against such acts, which we feel there is no need for using such excessive force against the Iraqis and against the citizens."
One man who said he witnessed the shooting said it appeared that the women in the car were frightened when the people in the security detail fired warning shots.
"What a shame," he said. "Maybe she got confused or she got scared, and when she got scared they frantically started shooting at them.
"Yes, they killed those two women. They were sitting in the front, ... and there were two kids. But the two kids, nothing happened to them," the man added.
Another witness to the shooting said the women were shot from a distance.
"It was a family, two women, one was driving and the second was a passenger," he said. "They killed them and they were at a far distance from them."
The Iraqi government has vowed to clamp down on private security firms, a resolve that emerged in the aftermath of the September 16 incident in Baghdad's Nusoor Square. That incident, involving Blackwater guards, left 17 civilians dead.
Under a provision put into place in the early days of the U.S.-led occupation of Iraq, security contractors have immunity from Iraqi law.
An Iraqi investigation into the incident called the shootings "premeditated murder" and the government plans to recommend that Blackwater pay $8 million to families of each of the 17 people killed.
Blackwater has said its contractors "acted lawfully and appropriately."
A joint U.S.-Iraqi committee met for the first time Sunday to begin reviewing security operations. It plans to issue a report offering recommendations to the Iraqi and U.S. governments aimed at making sure security company details don't endanger public safety.
Also Tuesday, two suicide truck bombs were detonated minutes apart in the northern Iraqi city of Baiji, killing at least 22 people and wounding 30. Police said it was a coordinated attack on anti-insurgent Sunni tribal leaders.
The first blast hit the home of Col. Saad al-Nufous, a tribal leader and the city's police chief. Al-Nufous was unharmed, although family members were among the casualties, police said.
The blast smashed all the home's windows and ripped its doors from their frames, The Associated Press reported.
"It was a really huge explosion. We panicked and ran out. But for minutes we couldn't see anything because of the heavy smoke," government employee Saleh Jassim Moussa, 38, told AP. "We're still digging through the rubble, looking for others."
The second bomb struck al-Rahim mosque as several tribal leaders were praying, said police. The blast targeted the city leader of the Salaheddin Awakening Council, a Sunni group that joined the fight against al Qaeda in Iraq, said an Interior Ministry official.
"This is yet another failed attempt to break the will of the Iraqi people who just want to go on with their lives without violence, raise their children, earn a living and coexist together in a peaceful manner," said U.S. military spokesman Lt. Col. Michael O. Donnelly, according to AP.
The attacks struck at about 6:30 a.m. (11:30 p.m. ET) and prompted Salaheddin provincial police to impose curfews. The province is located about 130 miles north of Baghdad.
Last week, a senior member of the Salaheddin Awakening Council, Sheik Muawiya Jebara, also was assassinated in a bombing outside Samarra. An al Qaeda in Iraq front group, the Islamic State of Iraq, claimed responsibility and threatened further attacks against those supporting the U.S.-led fight.
Tuesday's attacks came after two truck bombings targeted police stations in the province. Fourteen people were killed in a market north of Samarra and at least three died at a checkpoint blast outside Tikrit, according to provincial officials and authorities in Baghdad.
Violence also struck neighboring Nineveh province on Tuesday, where gunmen assassinated a provincial police official, and in Baghdad, where bombers killed 12 civilians in two incidents.
CNN's Jomana Karadsheh in Baghdad and Elise Labott contributed to this report.
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