Kabul: The US forces conducted a raid to destroy a cache of weapons north of Kabul early on Monday morning, a US Army spokesman said, giving rare details of unilateral activity in Afghanistan.
Afghan residents took to the streets in Parwan province in protest, briefly obstructing the highway to the capital.
Solo US operations are legal under a bilateral security agreement the two nations signed last year, but only in exceptional circumstances.
The raids remain a divisive subject in Afghanistan. They were a key reason then-President Hamid Karzai refused in 2014 to sign a deal allowing U.S. forces to stay in the country. President Ashraf Ghani signed the agreement as soon as he took office in September.
"US Forces conducted an operation ... to destroy a cache of munitions that could be used to conduct attacks against Afghans and Coalition Forces," public affairs director Colonel Brian Tribus said.
Little is known about the activities of US counter-terrorism troops that have been authorised to continue fighting the Taliban and other militants after the NATO combat mission officially ended last year.
Local authorities complained they had not been consulted ahead of time.
"As the operation was launched without coordination of local authorities, it made people angry," a spokesman for the governor, Wahid Sediqqi, said.
Around 9,800 US troops remain in Afghanistan, including around 3,000 who operate outside a NATO training mission that ends in 2016.
Afghanistan’s chief executive Abdullah Abdullah said the government had launched an investigation and promised to defend “the values of the jihad and the prestige of the mujahideen”.
US army spokesman Tribus said the operation was conducted in keeping with bilateral military agreements.
These include provisions to fight the Taliban and other militants, and protect coalition forces.
The weapons were stored at a house owned by former anti-Soviet mujahideen commander Jan Ahmad in Charikar district, according to the governor’s office in Parwan. The commander has not been linked to the insurgency and it was unclear how his cache of weapons posed a threat.
It is common for local powerbrokers in Afghanistan to raise their own private security forces.
Last month, the scope of such forces was visible when the government called on hundreds of local militiaman to help the police and army fight the Taliban in northern Kunduz province.
