Report: Two Americans killed in latest Afghan 'insider attack'

Tuesday's "insider attack" was the first carried out by a member of Afghanistan's nascent intelligence directorate, known as the National Directorate of Security.

The attack took place as Afghan and U.S. military officials were conducting a visit to the Afghan intelligence outpost in the Maruf district of Kandahar province in southern Afghanistan, according to The New York Times. 

During the visit, the Afghan intelligence officer detonated explosives he had concealed beneath his uniform, killing himself and six others, including the two U.S. officials. 

Also among the dead was Ghulam Rasool, the Afghan deputy director of intelligence for Kandahar province, along with two of his bodyguards and another Afghan intelligence officer, according to the Times

It remains unclear whether the suicide bomber acting alone or was a double agent working for the Taliban. 

The attack comes just as U.S. and Afghan intelligence officials are ratcheting up efforts to purge Talban infiltrators from the ranks of the Afghan National Security Forces (ANSF). 

U.S. military advisers have revamped the vetting process for ANSF recruits as a way to curb insider attacks against U.S. and NATO forces in country.

American and Afghan military commanders in Afghanistan also have implemented an aggressive counterintelligence strategy designed to pinpoint where and how Taliban operatives are working their way into the ANSF pipeline.

But until now, the threat of insider attack had come mostly from Afghan military and police, not its intelligence officers. 

Prior to Tuesday's attack, Afghanistan's military and intelligence leaders had been busily planting dozens of intelligence officers within the military and national police forces across the country to ferret out Taliban operatives or sympathizers.

Afghan intelligence officials have even gone so far as to ban all cellphones for new ANSF recruits as a way to limit potential communication between those recruits and Taliban commanders.

But despite the best efforts by Afghan and coalition leaders to stem the rise of insider attacks, there is no possible way to completely prevent them happening, Chairman of the Joint Chiefs of Staff Gen. Martin Dempsey said last Wednesday. 

"We can dramatically lower the numbers [of attacks] ... but we can't prevent it," Dempsey said during a speech at the National Press Club. 

More than 51 coalition troops, mostly from the United States, have been killed at the hands of their Afghan partners this year.