A Jordanian policeman shot into a group of fellow UN police officers in a prison compound in Kosovo, killing two Americans before being shot and killed in the ensuing gunbattle. Eleven others, including 10 Americans, were wounded.

A group of 21 American correctional officers, along with two Turks and an Austrian officer, were leaving the detention centre after a day of training in northern Kosovo on Saturday when they came under fire from at least one member of a group of Jordanians on guard at the prison, said Neeraj Singh, a UN spokesman. The officers shot back. In the 10-minute gun-battle, the attacker and two American officers were killed, while 10 more Americans and one Austrian were wounded.

It was not clear what touched off the incident. Four Jordanian police officers were arrested, a NATO source told AP on condition of anonymity.

"As far as we know, there was no communication between the officer who fired and the group of victims," Singh said. The motive remained unknown and authorities were investigating the circumstances.

Jordan's government expressed regret for the incident and stressed that it is following up on the investigation to uncover details of what had taken place, a statement carried by the official Jordanian Petra agency said. The statement identified the Jordanian UN police officer as Ahmed Mustafa Ibrahim Ali. UN and local police officers sealed off the yard of the well-protected detention center. They took pictures and marked the bullet cartridges with numbers. The body of a police officer, covered with what looked like a dark blue jacket, lay for hours in the yard of the prison compound where the shooting occurred. One witness, a 50 year-old woman, who spoke on condition of anonymity, said she heard the shooting, ran to her balcony overlooking the prison yard and saw one officer shooting and another hiding.

Another witness, a 31-year-old man, said he was at a nearby park when he heard the shooting and later heard American officers yelling, "Drop the gun! Drop the gun!"

"It is absolutely too early to draw any conclusions with regard to what happened there," the head of the UN police, Stefan Feller, told Associated Press Television News minutes after visiting the site. He called the shootout a "terrible incident".There are some 3,500 UN police officers serving in Kosovo alongside a 6,000-strong local force.

The shootout took place in Kosovska Mitrovica, a city that has long been the scene of ethnic violence between Serbs and ethnic Albanians, including riots that broke out a month ago, killing 19 and injuring 900.

The top U.N. official in Kosovo, Harri Holkeri, seemed stunned at the shooting incident, which occured as the mission is still trying to recover from last month's violence.

"I am deeply shocked and dismayed at the unfortunate death of dedicated professionals who have come such a great distance to help Kosovo on its road to future," he said.

Kosovo became a UN protectorate in 1999, after NATO launched a 78-day air war to stop former President Slobodan Milosevic from cracking down on ethnic Albanians seeking independence.