Taliban fighters overran an army base in northern Afghanistan, officials said on Tuesday, killing at least 17 soldiers.
Dozens more are feared captured in what is seen as a stinging blow to the security forces already struggling to push insurgents from eastern Ghazni.
The fall of the base — known as Camp Chenaya — in the Ghormach district of volatile Faryab province, came with security forces already stretched by the days of fighting in Ghazni, a strategic provincial capital two hours from Kabul.
Security forces have struggled to hold back the Taliban since Nato combat troops pulled out of the country in 2014.
The Taliban gained control of the base after days of heavy fighting, according to army spokesman for northern Afghanistan, Mohammad Hanif Rezaee.
He said about 100 soldiers were on the base when it was attacked on Sunday.
"It is a tragedy that the base fell to the enemy. Some soldiers were killed, some captured and some fled to nearby hills," Mr Rezaee told AFP.
At least 17 soldiers were killed in the attack, according to defence ministry spokesman Ghafoor Ahmad Jawed, while a local MP said Taliban fighters captured another 40 in the base.
"Preparations are under way to launch an operation to recapture the base," said the ministry's spokesman.
Tahir Rehmani, head of Faryab's provincial council, said it fell after the soldiers begged for reinforcements and air support from Kabul but were ultimately ignored.
"They were too busy with Ghazni," said Mr Rehmani.
Ghazni, further east, was attacked by the Taliban on Thursday, but remains in government hands, officials said.
Fears of civilian casualties in the city, however, were growing as Afghan security forces backed by United States air power struggled to push the Taliban out, five days after the assault began.
Analysts have said the insurgents may be seeking to demonstrate strength as they come under increasing pressure to join peace takls after the ceasefire during Eid in June.
"Clearly the Taliban have paid no heed to the calls of the Afghan people for them to reconcile and join the peace process," US spokesman Lt Col Martin O'Donnell said on Tuesday.
The assault on Ghazni and the fall of the Chenaya base also illustrate how stretched Afghan forces are across the country, said analyst Abdul Hamid Sofof.
"The Taliban know this and they make Afghan forces fight on several fronts, making them run thin," said Sofof.