KABUL, AFGHANISTAN - A wave of betrayal has left at least 17 Afghan policemen dead in the past 10 days -- all slain in their sleep, at the hands of those close to them.

In the very early hours Thursday, an Afghan policeman unlocked the door of the post where he was stationed in Oruzgan Province and let in his friends from the Taliban, who with knives and guns helped him kill four and wound eight of his sleeping colleagues.

On Sunday, a police commander in the remote northern province of Jawzjan shot to death, in their beds, five of the men under his command, and fled to join the Taliban.

And on Dec. 18, a teenager apparently being kept for sexual purposes by an Afghan Border Police commander in southern Kandahar province drugged the commander and 10 policemen at the post to put them to sleep, then shot them all; eight died and three survived.

In the crisis that has risen in the past year over insider killings, when Afghan security forces turn on their allies, the toll has been heavier for the Afghans themselves -- at least 86 in a count by the New York Times this year -- than for U.S. and other NATO forces, who have lost at least 62 so far this year.

Unlike most insider attacks against foreign forces, known as "green-on-blue" killings, most of the attacks between Afghans, "green on green," have been clear cases of either infiltration by Taliban insurgents or turncoat attacks. As with the three recent attacks, they have fallen most heavily on police units, and they have followed a familiar pattern: The Taliban either infiltrate someone into a unit or win over someone already in a unit, who then kills his comrades in their sleep. Frequently, the victims are first poisoned or drugged at dinner.

The most recent attack took place Thursday in Tarin Kowt, in southern Afghanistan. According to a police spokesman, an officer named Hayat Khan, who had been in regular touch with the Taliban for religious guidance, waited until the other officers at his checkpost fell asleep and then called Taliban fighters by cellphone and let them in. The attackers stabbed the one officer on watch, but he raised the alarm in time to wake up some of the others.

In the ensuing firefight, four policemen were killed and eight wounded, while Khan and his Taliban confederates managed to escape, according to the spokesman's account.

In some cases, personal grievances may be a factor. That is apparently what happened in the case of a young man who police say killed eight border security police in their check post near Spinbaldak on Dec. 18. Police said the man had been the involuntary companion of the border police commander at that checkpost for several years.

The night of the attack, the man offered to make a special dinner for the police. He and two friends put drugs in the food and then shot everyone there, including the commander, escaping across the border, a police official said.