Afghan security forces recaptured Yamgan district of Badakhshan Province from the Taliban after four year in September 2019.
Afghan officials say hundreds of foreign combatants are fighting alongside Taliban militants in a strategic northern province, a move that if proven true would violate the terms of the U.S.-Taliban peace agreement.
Zakaria Sawda, the governor of the northeastern province of Badakhshan, said around 400 foreign militants, mostly from neighboring Tajikistan and Uzbekistan, had joined the Taliban and were fighting Afghan security forces in the province.
Sawda told RFE/RL that the Taliban and foreign fighters were attempting to create a large terrorist "hub" in Badakhshan, adding that it was a "serious concern."
Sawda's claims could not be independently verified. But if confirmed, the Taliban's actions would constitute a violation of the agreement the militant group signed with Washington in February.
Under that deal, the Taliban committed to severing ties with terrorist groups and preventing terrorists from using territory under its control to launch attacks against the United States and its allies, including the Afghan government.
In exchange for the Taliban's counterterrorism guarantees, the United States agreed to withdraw all of its around 12,000 troops from Afghanistan by July 2021.
There was no immediate comment from the Taliban, which controls and contests large parts of Badakhshan, a remote, mountainous province bordering Tajikistan, China, and Pakistan.
Sawda said some 30 foreign fighters entered Badakhshan on April 14, although he did not specify how the militants had come and from where.
He said the foreign combatants were fighting Afghan forces in the districts of Warduj, Jurm, and Yamgan -- Taliban strongholds in the province.
Sawda said the foreign fighters also included combatants from China's northwestern region of Xinjiang and Russia's North Caucasus region of Chechnya.
Bashir Ahmad Samim, the head of the provincial council in Badakhshan, said foreign fighters in the province had also joined Islamic State (IS) militants.
"Foreign terrorists are conducting the war" in several districts, Samim said.
Taliban and IS militants have clashed in various parts of Afghanistan, although the two Sunni extremist groups have also fought together on occasion.
Foreign militants have been present in Afghanistan for years. Many are believed to have arrived after fleeing a Pakistani military offensive in 2014 in that country's restive tribal areas, a former stronghold of the Pakistani Taliban, Al-Qaeda, and other regional militant groups.
The foreign fighters sought sanctuary in Afghanistan amid a drawdown of international forces at the end of 2014.
In northern Afghanistan, some of the foreign fighters have joined the Taliban and other militant groups. They include the Islamic Movement of Uzbekistan, some of whose fighters have claimed allegiance to the IS group.