Kabul, Afghanistan ? British peacekeepers opened fire in Afghanistan’s capital for the third time in two weeks, shooting at a lone gunman who attacked their observation post, the international peacekeeping force said Thursday.

No injuries were reported to either peacekeepers or the gunman in Wednesday’s attack, which targeted eight British troops manning an observation post in the southwest of Kabul, said Graham Dunlop, a spokesman for the 18-nation peacekeeping force.

In northern Afghanistan, tensions flared between two rival commanders in Afghanistan’s interim government, with one threatening to attack if his rival refused to recall tanks and troops from his territory.

Keeping peace between ethnically divided warlords, despite power and turf battles, stands as one of the largest challenges facing Afghanistan’s fledgling government.

In Kabul, there was no information on the identity or motive of the gunman who fired on the British forces. The attack, like one on Feb. 20, occurred near the rocket-ruined Darulaman palace, a former residence of Afghanistan’s royalty.

“One gunman was seen firing, and then he was seen running away, and then he fired again,” Dunlop said.

One bullet hit the roof of the observation post.

The most serious shooting involving peacekeepers here occurred Feb. 16, when British peacekeepers fired on a vehicle taking a pregnant woman to the hospital. The vehicle was on the streets after curfew. The woman’s brother-in-law was killed.

The peacekeepers, who fired 60 rounds at the vehicle, said someone from the vehicle opened fire first. The woman denied their claim, and Afghanistan’s interim administration is investigating.

Two peacekeepers involved in the shooting have since returned to Britain.

The peacekeepers say they now have ambulances available and a communication system in place with the Afghan police to identify Afghan residents in need after the curfew, which begins at 10 p.m.

In the Feb. 20 shooting, British and Afghans on a joint patrol returned fire after coming under attack, the international force says.

The British lead an 18-country contingent of peacekeepers in Kabul, with a total force of 4,500.

They conduct joint patrols with Afghans in an attempt to provide security in the capital, shattered by two decades of relentless war.

In northern Afghanistan, ethnic Tajik leader Atta Mohammed accused rival Gen. Rashid Dostum, an ethnic Uzbek, of sending six tanks and dozens of troops into Shulgara, 50 miles southwest of the main northern city of Mazar-e-Sharif.

The move could not be immediately confirmed. Sporadic fighting between soldiers under the control of the two leaders has killed dozens of people in recent weeks.

Atta said he had demanded that Dostum’s local commander recall his troops to a Dostum-controlled barracks in the area. If an agreement could not be reached peacefully, Atta warned, he may attack to force Dostum’s troops back.

“We are trying to solve it in a brotherly way,” Atta told The Associated Press. “But if we cannot, then we must defend our poor people in the village.”

Atta claimed Dostum’s troops were harassing Tajiks in the area. Tajiks, Uzbeks and other ethnic groups live together in the district, which is controlled by Atta.

Atta said he had informed government officials in the capital, Kabul, and U.S. special forces representatives in the north about the dispute.

Dostum is currently out of Afghanistan and is believed to be in Turkmenistan, where he keeps a house. Spokesmen for Dostum at his Afghan base of Shibergan and in Mazar-e-Sharif could not be immediately reached for comment.

Both leaders are members of the U.N.-brokered interim government of Prime Minister Hamid Karzai, but relations have been rocky between the factions since coalition forces ousted the Taliban.

Earlier this week, Atta and one of Dostum’s senior lieutenants signed a peace agreement in another northwestern village where fighting the week before killed at least six people.

In other developments:

 Claims are arriving daily about the whereabouts of ex-Taliban leader Mullah Mohammad Omar, keeping U.S. search teams “very busy, day and night,” said Ahmed Wali Karzai, a military council member in Kandahar, Omar’s former stronghold.

Some say Omar’s party is in the central mountains, “then the next day they’re in Iran, then Peshawar (Pakistan),” said Karzai, brother of new Afghan leader Hamid Karzai. No trace of the fugitive cleric has been reported found thus far.

 U.S. officials are turning to modern forensic science _ DNA testing _ in hopes of determining whether Osama bin Laden is dead or alive.

Government sources said Wednesday that officials want to compare human remains found at bombing sites in Afghanistan with DNA samples from the terrorist leader’s family. A New York spokesman for bin Laden’s family said he was unaware of the government making any formal request for samples.