The capture of the base in remote Badakhshan province came Saturday evening after four days of fighting, said Abdullah Nazari, chairman of the provincial council.
As in previous instances of Afghan forces losing ground to Taliban insurgents this summer, Nazari said that government soldiers put up a fight but received no backup from the central government.
"No one has told us why yet, but we expect an answer as to why our own security forces were left to fight alone for four days," Nazari said. "The ministries of Interior and of Defense must both provide answers."
Dozens of soldiers were killed or injured in the fighting in Warduj district, Nazari added.
The district governor in Warduj, Dost Mohammad, said 15 border police were killed in the fighting, which began Thursday and lasted until 5 p.m. Saturday afternoon, when the base was surrendered.
He said they fought for three days straight.
On Sunday, all of the detained security forces, more than 100, he said, were released by the Taliban.
Sources speaking to local media said several Afghan Local Police – a U.S.-backed government militia – and Afghan Border Protection Police stationed in and around the Teergaran base surrendered and handed over their weapons to the Taliban.
The base is in central Badakhshan, a mountainous province situated between Pakistan and Tajikistan. The strategic location of the base gives those inside the access to maintain security of the entire district in central Badakhshan.
Acting provincial governor Shah Waliullah Adeeb said he warned that if backup did not arrive, the base and Afghan forces were at risk. As the base was being besieged by at least 100 Taliban fighters, a border police commander made an agreement with the Taliban that led to the capture of 107 local and national police officers, Adeeb said.
In online statements, the Taliban confirmed the raid and claimed to have inflicted dozens of casualties on Afghan forces.
The fighting comes days before representatives of the Taliban and the Afghan government are set to meet in China for the second face-to-face talks aimed at reaching a peace agreement to end more than a decade of conflict.
As in the previous meeting earlier this month in Pakistan, U.S. and Chinese officials are also expected to attend as observers.
Although the talks have been endorsed by Mullah Mohammad Omar, the Taliban's Pakistan-based leader, some factions within the militant organization are believed to oppose negotiating with the Kabul government, which they deride as a tool of U.S. interests.