The secretive militias, whose support from America's Central Intelligence Agency is originally rooted in the Soviet-Afghan war of the 1980s, have long hunted the Taliban across Afghanistan and have seen increasing action as the war against the insurgents intensifies.

Human Rights Watch (HRW) documented 14 cases from late 2017 to mid-2019 in which it said CIA-backed "strike groups" committed serious abuses during night raids, such as one in the southeastern province of Paktia in which a paramilitary unit killed 11 men, including eight who were home for the Eid holidays.

In many cases, the raids -- usually in Taliban-controlled areas -- were accompanied by air strikes that "indiscriminately or disproportionately" killed civilians, HRW said in a report.

Sometimes, troops detained men and didn't tell families where they were being held.

Night raids -- where special forces troops blast doors and rush a building under the cover of dark -- are a popular tactic that combines surprise, overwhelming firepower and night-vision equipment to stun occupants.

"In ramping up operations against the Taliban, the CIA has enabled abusive Afghan forces to commit atrocities including extrajudicial executions and disappearances," said Patricia Gossman, the report author and HRW's associate Asia director.

"In case after case, these forces have simply shot people in their custody and consigned entire communities to the terror of abusive night raids and indiscriminate air strikes."

- 'Death squads' -

Afghan authorities and US forces have increased the use of paramilitary groups to combat a resurgent Taliban that has been hammering Afghanistan's beleaguered national security forces.

Part of the National Directorate of Security (NDS), paramilitary forces do not fall under normal command chains and so have less oversight.

Speaking to HRW, one diplomat referred to them as "death squads."

Afghan militias have largely been recruited, trained, equipped, and overseen by the CIA, according to the rights watchdog.

Ties date back to the 1980s, when the CIA was funnelling money and equipment to Afghan rebels and mujahideen fighting Soviet troops.

After a lull during the Taliban regime in the 1990s, the CIA re-established ties with warlords and militias fighting the insurgency following the September 11, 2001 attacks.

The CIA did not immediately respond to a request for comment.

According to the Special Inspector General for Afghanistan Reconstruction (SIGAR), a US government watchdog, Afghan special forces conducted 2,531 ground operations from January-September this year, more than the total of 2,365 for all of 2018.

A UN report earlier this month found an unprecedented number of civilians was killed or wounded in Afghanistan from July to September this year.

The tally -- 1,174 deaths and 3,139 injured from July 1 until September 30 -- represents a 42 percent increase over the same period last year.