Taliban fighters overran an army base in northern Afghanistan, officials said on Tuesday, killing at least 17 soldiers with dozens feared captured in a stinging blow to security forces already struggling to push insurgents from eastern Ghazni.

The fall of the base in Ghormach district of volatile Faryab province came with security forces — who have struggled to hold back the Taliban since NATO combat troops pulled out in 2014 — already stretched by the days of fighting in Ghazni, a strategic provincial capital two hours from Kabul.

Militants gained control of the base after days of heavy fighting, according to army spokesman for northern Afghanistan Mohammad Hanif Rezaee.

He said around 100 soldiers were on the base when it was first 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,” Rezaee told AFP.

At least 17 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, known as Chenaya.

“Preparations are underway to launch an operation to recapture the base,” said the ministry's spokesman.

Tahir Rehmani — head of Faryab's provincial council — said the base fell after the soldiers begged for reinforcements and air support from Kabul but were ultimately ignored.

“They were too busy with Ghazni,” said Rehmani.

Ghazni, further east and which the Taliban first assaulted late on Thursday, remains in government hands, officials have said.

But fears of civilian casualties in the city were growing as Afghan security forces backed by US air power struggled to push the Taliban out five days after the assault began.

A spokesman for US Forces in Afghanistan, Lt Col Martin O'Donnell, said there had been “no reported enemy activity” so far on Tuesday, though he added that “some Taliban forces remain in the city”.

With reports of fighters hiding among the civilian population, O'Donnell said residents had been “terrorised and harassed”.

“The Taliban, who falsely and repeatedly claim that they do not target civilians, have executed innocents, destroyed homes, burned a market and created the conditions for a potential humanitarian crisis with this attack,” he said.

The United Nations said unverified reports put civilian casualties at more than 100, with residents also at risk from several days of US air strikes.

O'Donnell said no air strikes had been carried out yet on Tuesday.

Bombs placed along the road leading north and south from the city also “prevented civilians from safely fleeing the violence”, said a UN report.

Communication networks remained largely down in Ghazni, making any information difficult to verify. But residents said the violence continued.

“Ghazni is a ghost city now. The Taliban are going from house to house to find government officials or their relatives to kill,” said one resident, Sayed Zia.

“Those who can are fleeing.” Another resident also said the Taliban were killing civilians who refused to help them.

“I saw two trucks full of coffins going toward a cemetery in the city. They all seemed to be civilians,” said Abdullah, who asked to only use one name.

“The city is full of smoke. Everywhere they go they set the places on fire,” he said, adding that shops were being looted, with water and food scarce.

'Let us go home'

On Monday, the Afghan defence minister said at least 100 security forces had been killed in the fighting in Ghazni so far.

Afghan security forces, beset by desertions and low morale, have suffered staggering casualties in recent years.

Analysts have said the insurgents may be seeking to demonstrate strength as they come under increasing pressure since an unprecedented ceasefire in June to join peace talks.

“Clearly the Taliban have paid no heed to the calls of the Afghan people for them to reconcile and join the peace process,” the US spokesman 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.

The insurgents have overrun provincial capitals before, including western Farah in May and northern Kunduz in 2015. Each time, they failed to hold the city, pushed out by security forces within days.

Ghazni lies along the major Kabul-Kandahar highway, effectively serving as a gateway between the capital and the militant strongholds in the south.

Hundreds of people trying to reach Kabul from Iran and other provinces were stranded at a bus station in southern Kandahar Tuesday, unable to travel further due to the fighting, an AFP reporter there said.

Some said they had been stuck for days, and were running out of money and food.

“For God's sake,” one man told AFP. “Stop fighting and let us go home.”