A private security guard fatally shot an Iraqi taxi driver, Iraqi officials said Monday, in the latest incident involving what Iraqis believe are unprovoked killings by contractors hired to protect Americans.

U.S. Embassy spokesman Philip T. Reeker said DynCorp International, a Falls Church, Va.-based company, reported a "security incident" Saturday involving one of its teams and that the embassy's regional security office was "following this closely."

But Reeker could not confirm any details of the incident, including whether anyone was killed or wounded.

"These are very upsetting incidents for everyone involved," Reeker told reporters.

DynCorp International is among three firms — along with Blackwater Worldwide and Triple Canopy — under contract to protect American diplomats and other officials in Iraq.

Iraqi officials said the shooting took place Saturday at 12:45 p.m. across from a children's playground in Baghdad's Atafiyah neighborhood, when a taxi driver pulled up close to a convoy of seven U.S. vehicles driving through the area.

Security personnel signaled for the taxi to pull away, and then one of the guards opened fire on the car, they said.

The driver was shot in the chest and head, but was still alive when local shopkeepers and police rushed to help him, witnesses and police said. He died in a police car on the way to the hospital, said Ahmed Adel, a barber who watched the events unfold outside his shop.

"The convoy stopped at an intersection where there was little traffic jam. ... Suddenly, guards from the last SUV opened fire on the taxi while it was totally motionless and no threat whatsoever to the convoy," Adel said. "We rushed to the car and helped the police pull him out."

He added that the taxi's gearshift was in neutral when they pulled the driver out, suggesting that his car was not moving when he was shot.

Afterward, police searched the taxi and found no weapons or other signs of threatening activity, police and the Interior Ministry said. The convoy did not stop for the investigation, an officer said on condition of anonymity because he was not authorized to release information.

Another witness said that after the shooting, a guard stepped out of the last vehicle in the convoy — from which the shots were fired — and walked over to the taxi to see what had happened, but then turned back quickly.

"They simply did not care about the shot taxi driver, and the convoy sped away," the man said, refusing to give his name because of the situation's sensitivity.

The shooting occurred on an exit ramp next to a bridge spanning the Tigris River. Atafiyah is a mixed Sunni-Shiite neighborhood that has not seen as much violence as other Baghdad enclaves. Piles of soft drink cans and other groceries line sidewalks outside dozens of retail shops.

It was the latest shooting by private security contractors perceived by many here as operating above the law. The U.S. government has offered some guards limited immunity under deals that have slowed prosecution of other shooting cases and angered Iraqis.

In September, another shooting left 17 Iraqis dead and prompted the Iraqi government to call for the expulsion of the firm involved, Blackwater Worldwide. The company has said its convoy was under attack before it opened fire, but initial investigations by Iraqi and U.S. authorities have concluded otherwise.

Iraq's Interior Ministry immediately opened an investigation into Saturday's shooting, said spokesman Maj. Gen. Abdul-Karim Khalaf.

The incident came just two days before the arrival of two top U.S. officials sent from Washington to investigate the role of private security companies in Iraq.

Last month, Secretary of State Condoleezza Rice ordered new measures to improve government oversight of bodyguards, including tighter rules of engagement and a board to investigate any future killings.

The steps would also require contractors to undergo training intended to make them more sensitive to Iraqi culture and language.

The changes to rules of engagement would bring the State Department closer to military rules, although the moves will not have much visible effect on the way private guards operate in Baghdad and elsewhere in Iraq.

Gregory Starr, acting assistant secretary of state for diplomatic security, and P. Jackson Bell, deputy under secretary of defense for logistics and materiel readiness, arrived in Baghdad on Monday to help implement the new rules, Reeker said.

Meanwhile, violence continued Monday, but at drastically reduced levels from several months ago. At least 13 people were killed or found dead across Iraq, including five bodies found in Baghdad, police and morgue officials said.

The U.S. military issued tallies of mortar and rocket attacks across the country, saying October's total marked a 21-month low.

Last month saw 369 "indirect fire" attacks — the lowest number since February 2006. October's total was half of what it was in the same month a year ago. And it marked the third month in a row of sharply reduced insurgent activity, the military said.