KABUL, Afghanistan (AP) — An Afghan soldier shot and killed two British troops Monday at a NATO coalition base in southern Afghanistan before being gunned down by international forces, officials said.

The attack was the latest in a string of so-called “green on blue” attacks in which Afghan security forces have turned their guns on their international colleagues or mentors. Such attacks have become increasingly common over the past year, particularly since the burning of Qurans at a U.S. base in February.

Fifteen NATO service members, including eight Americans, have been killed by Afghan security officials or militants disguised in their uniforms so far this year.

Monday’s shooting occurred around 11 a.m. in front of the main gate of a joint civilian-military base in Lashkar Gah, the provincial capital of Helmand province, the governor’s office said.

Ghulam Farooq Parwani, deputy commander of the Afghan National Army in Helmand, said the shooter was from the eastern Nangarhar province and had been in the army for four years. The Afghan soldier arrived at the gate of the base in an army vehicle. He was able to get close to the British troops by claiming that he had been assigned to provide security for a delegation of government officials from Kabul who were visiting the base Monday, according to Parwani.

“He got close to the foreign troops – three or four metres (yards) – and he opened fire,” Parwani said. “Then the foreign troops killed him.”

Taliban spokesman Qari Yousef Ahmadi said the shooter was an Afghan soldier who was in close contact with insurgents and had notified the Taliban of his planned attack before carrying it out.

Since 2007, Afghan security forces have killed an estimated 79 NATO service members and wounded more than 110 others, according to the Pentagon. More than 75 percent of the attacks have occurred in the past two years.

A Western official in southern Afghanistan confirmed that the attack happened at the main NATO base in Lashkar Gah, Helmand province but declined to give further information. The official spoke on condition of anonymity because the information had not been officially released.

Monday’s attack also comes two weeks after a U.S. soldier allegedly went on a pre-dawn shooting rampage in neighbouring Kandahar province, killing 17 people and wounding six.

British Defense Secretary Philip Hammond confirmed the two killed were British service members.

“Details of the incident are still emerging but it appears that a member of the Afghan National Army opened fire at the entrance gate to the British headquarters in Lashkar Gah,” Hammond told the Commons. “Our thoughts, as ever, are with their families, for whom this will be a deeply personal tragedy.”

The killings come at a time when international troops have stepped up training and mentoring of Afghan soldiers, police and government workers so that Afghans can take the lead and the foreign forces can go home.

The success of the partnership, which is the focus of the U.S.-led coalition’s exit strategy, is threatened by the rising number of Afghan police and soldiers – or militants disguised in their uniforms – who are turning their guns on their foreign allies.

Six American troops were killed in what were believed to be revenge attacks for the burning of the Qurans, although it is impossible to know the exact motive because most the shooters were killed in the incidents.

On March 1, two U.S. troops were killed by two Afghan soldiers and an accomplice on a joint U.S.-Afghan base in Zhari district of Kandahar province in the south.

On Feb. 25, two U.S. military advisers were found dead with shots to the back of the head inside the Afghan Interior Ministry in Kabul.

Two U.S. troops were killed Feb. 23 by an Afghan soldier during an anti-Western protest in Nangarhar province in eastern Afghanistan over the Quran burning.

The U.S. apologised for the burning, saying the Islamic texts were mistakenly sent to a garbage burn pit Feb. 20 at Bagram Air Field, north of Kabul. But the incident raised what had been simmering animosity toward outsiders to a full boil. Deadly protests raged around the nation for six days – the most visible example of a deep-seated resentment bred by what Afghans view is a general lack of respect for their culture and religion.