KABUL, Afghanistan -- Afghan Army Sgt. Habibullah Hayar didn't know it, but he had been sleeping with his enemy for weeks.
Twenty days ago, one of his roommates was arrested on charges of allegedly plotting an insider attack against their unit, which is partnered with NATO forces in eastern Paktia province.
Afghan soldiers and policemen -- or militants in their uniforms -- have gunned down more than 50 foreign troops so far this year, eroding the trust between coalition forces and their Afghan partners. An equal number of Afghan policemen and soldiers also died in these attacks, giving them reason as well to be suspicious of possible infiltrators within their ranks.
"It's not only foreigners. They are targeting Afghan security forces too," said the 21-year-old Hayar, who was in Kabul on leave. "Sometimes, I think what kind of situation is this that a Muslim cannot trust a Muslim -- even a brother cannot trust a brother. It's so confused. Nobody knows what's going on."
The attacks are taking a toll on the partnership, prompting the U.S. military to restrict operations with small-sized Afghan units earlier this month.
The close contact -- with coalition forces working side by side with Afghan troops as advisers, mentors and trainers -- is a key part of the U.S. strategy for putting the Afghans in the lead as the U.S. and other nations prepare to pull out their last combat troops at the end of 2014, just 27 months away.
The U.S. military also has shown increasing anger over the attacks.
"I'm mad as hell about them, to be honest with you," Gen. John Allen, the top commander of U.S. and NATO forces in Afghanistan, told CBS' "60 Minutes" in an interview scheduled to be broadcast on Sunday. "It reverberates everywhere across the United States. You know, we're willing to sacrifice a lot for this campaign, but we're not willing to be murdered for it."
So far this year, 51 foreign troops -- at least half of them Americans -- have been killed in insider attacks. The Afghan government has not provided statistics on the number of its forces killed in insider attacks. However, U.S. military statistics obtained by The Associated Press show at least 53 members of the Afghan security forces had been killed as of the end of August.
A U.S. military official disclosed the numbers on condition of anonymity because he said it was up to Afghan officials to formally release the figures. An Afghan defense official who was shown the statistics said he had no reason to doubt their accuracy.
Overall, the statistics show that at least 135 Afghan policemen and soldiers have been killed in insider attacks since 2007. That's more than the 118 foreign service members -- mostly Americans -- killed in such attacks since then, according to NATO.
Typically, foreign troops are the main targets, but Afghan forces also have been killed by comrades angry over their collaboration with Westerners and many more get killed in the crossfire, Defense Ministry spokesman Gen. Zahir Azimi said. He said the ministry did not have a breakdown of how many had been targeted or killed in gunbattles during the attacks.
In at least one instance, an Afghan police officer with alleged ties to militants, killed 10 of his fellow officers on Aug. 11 at a checkpoint in southwestern Nimroz province. An Afghan soldier also was killed on April 25 when a fellow soldier opened fire on a U.S. service member and his translator in Kandahar province, the southern birthplace of the Taliban.
Last year, a suicide bomber in an Afghan police uniform blew himself up May 28 in Takhar province, killing two NATO service members and four Afghans, including a senior police commander. And just a week before that, four Taliban fighters wearing suicide vests under police uniforms attacked a government building in Khost province, triggering a gunbattle that left three Afghan policemen and two Afghan soldiers dead. On April 16, an Afghan soldier walked into a meeting of NATO trainers and Afghan troops in Laghman province, blew himself up, killing five U.S. troops, four Afghan soldiers and an interpreter.
"It's difficult to know an attacker from a non-attacker when everybody is wearing a uniform, Hayar said.
The attacker was one of seven people rounded up earlier this month from various units within the Afghan National Army Corps 203, Hayar said. The corps covers the eastern Afghan provinces of Paktia, Paktika, Ghazni, Wardak, Logar and Khost.
"He was together with me in my room with some of my other colleagues. He had a long beard. We didn't know anything about him. We were living together, sleeping together," said Hayar, who has been in the Afghan army for 2 1/2 years.
He said the suspected infiltrator was identified after a Taliban militant arrested in Logar told his Afghan interrogators that members of the fundamentalist Islamic movement had infiltrated the corps and were planning imminent attacks. That prompted Hayar's superiors to start questioning soldiers in various units.
Hayar said his roommate's uneasy reaction raised suspicion, and investigators found Taliban songs saved to the memory card of his cellphone. He was then detained by Afghan intelligence officials and confessed he was a member of the Taliban and planned to stage attacks.
Hayar says he assumes his former bunkmate was probably going after foreign forces, but it makes him uncomfortable nevertheless.
"It's very hard to trust anybody -- even a roommate," he said. "Whenever I'm not on duty, I lock my weapon and keep the key myself. I don't put my weapon under my pillow to sleep because maybe someone will grab it and shoot me with my own weapon."
To counter such attacks, the U.S. military earlier this year stopped training about 1,000 members of the Afghan Local Police, a controversial network of village-defense units. U.S. commanders have assigned some troops to be "guardian angels" who watch over their comrades even as they sleep. U.S. officials also recently ordered American troops to carry loaded weapons at all time, even when they are on their bases.
Then, after a string of insider attacks, Allen this month restricted operations carried out alongside with small-sized Afghan units. Coalition troops have routinely conducted patrols or manned outposts with small groups of Afghan counterparts, but Allen's directive said such operations would no longer be considered routine and required the approval of the regional commander.
For their part, Afghan authorities have detained or removed hundreds of soldiers as part of its effort to rescreen its security forces. The Ministry of Defense also released a 28-page training booklet this month that advises soldiers not to be personally offended when foreign troops do things Afghans view as deeply insulting.
The booklet urges them not to take revenge for foreign troops' social blunders, such as blowing their noses in public, stepping into a mosque with their shoes on, walking in front of a soldier who is praying or asking about their wives.
"Most of the coalition members are interested to share pictures of their families. It is not a big deal for them. If someone asks you about your family, especially the females in your family, don't think they are disrespecting you or trying to insult you," the booklet says.
"That is not the case. By asking such questions, they are trying to show that they want to learn more about you. You can very easily explain to them that nobody in Afghanistan would ask, especially about wives or females in the family."