This image from video AP obtained from the SITE Intel Group on Sept. 15, 2012, purports to show smoke rising over Camp Bastion in Helmand Province, Afghanistan after what the Taliban media unit says is an attack at the base. (Uncredited/AP)

Two troops belonging to the U.S.-led military coalition were killed Saturday when an Afghan policeman turned his weapon on them in southern Afghanistan, NATO officials said. The latest insider attack underscored the continued vulnerability of international troops despite intense efforts by U.S. and Afghan leaders to stem the killings.

The casualties in southern Helmand province brought to 47 the number of coalition forces killed by their Afghan partners this year, most of them Americans. The shooting deaths have increasingly sown mistrust and strained the partnership between Afghan and Western forces battling the Taliban insurgency.

The province’s deputy police chief, Ismail Hotak, identified the dead troops as British and said four other troops were wounded.

The Afghan shooter was killed by another soldier at the scene in the town of Gereshk, Hotak said. Since 2007, when the insider- attack phenomenon began, about 105 international troops have been killed by rogue Afghan security forces.

The perpetrator was believed to be a member of the 16,000-member Afghan Local Police, the smallest component of the 352,000-strong Afghan national forces. The police are based in towns and villages and act as a sort of militia, partnered with U.S. Special Forces.

The U.S. military recently suspended training of 1,000 new Afghan Local Police recruits and has been revetting the existing ranks.

The shooting came on the same day that the Taliban asserted responsibility for an attack Friday night against a British base, Camp Bastion, also in Helmand province, that killed two U.S. Marines and wounded several other troops.

The Associated Press reported late Saturday that coalition officials said the attackers at Camp Bastion wore U.S. Army uniforms and destroyed six Harrier fighter jets. They said there were about 15 insurgents, 14 of whom were killed and one captured, AP reported.

Camp Bastion is adjacent to Camp Leatherneck, the site of U.S. Marine operations in Helmand.

The Taliban issued statements saying the assault was meant to avenge an anti-Muslim video that has sparked days of riots in more than 20 countries. But the militants also said the base attack was aimed at Prince Harry, a helicopter gunner who serves at Camp Bastion.

The prince, known as Capt. Harry Wales, was never in danger, the allied coalition said.

Last week, the Afghan army said it had arrested or expelled hundreds of its soldiers because of deficient documentation and links to insurgents. Afghan officials said they have undertaken a massive rescreening process to weed infiltrators and potential turncoats from the ranks.

The U.S. exit plan from Afghanistan relies on Afghan forces taking responsibility for the country’s security by the end of 2014. But the spate of insider attacks has raised serious, persistent questions about the loyalty of the Afghan forces to the U.S.-supported government as the war enters its 11th year. The attacks account for 14 percent of coalition casualties this year, up from 6 percent last year, according to analysts at the Long War Journal.

To reduce the threat, the United States has been helping the Afghan Defense and Interior ministries rescreen all forces. It has also stepped up counterintelligence operations within units and introduced cultural sensitivity training to help Afghans better understand that some perceived slights by coalition members are unintentional.

But U.S. military leaders also say arguments and grudges are simply more likely to escalate to fatal violence in Afghan society.

“We all recognize that this is a society that’s really been traumatized by 30-plus years of war,” Army Lt. Gen. James Terry, deputy commander of U.S. Forces­ Afghanistan, said at a briefing last week. “It also has a gun culture out there, and we also understand that a lot of grievances and dispute resolution are done, frankly, at the barrel of a gun.”