Bagram Air Base, hub of the United States forces in Afghanistan for 20 years until they withdrew last week, buzzed again with activity on Monday as Afghan forces settled into the vast premises, complete with its runways, barracks, control towers and hospital.

American troops handed the base over to Afghan security forces to bring an effective end to the longest war in US history, following an agreement with the insurgent Taliban last year.

"They (Americans) are completely out now and everything is under our control, including watchtowers, air traffic and the hospital," a senior Afghan government official told Reuters.

Reuters journalists on Monday visited the heavily fortified compound, long a symbol of Western forces deployed to shore up the Afghan government against the Taliban's campaign to regain power after being toppled by a US intervention in 2001.

Dozens of vehicles left behind by the United States stood on the premises while others zipped around with Afghan officials and personnel looking to come to terms with the magnitude of operating the vast base.

Radars oscillated as soldiers stood on guard, and hundreds of Afghan security personnel moved into barracks that once housed US soldiers.

Where American entertainers had once visited to boost the morale of US troops, an Afghan soldier strummed a guitar, singing a Pashto language epic on the Afghan homeland, while other Afghan soldiers toured the grounds on bicycles.

Read: Western forces pack up to end their war, Afghans 'manage the consequences'

Outside the walls of the vast base, things are not as serene. The Taliban have ramped up offensives against Afghan government forces across the country, particularly in the north where insurgents have gained territory rapidly.

On Sunday, hundreds of members of the Afghan security forces fled to refuge in neighbouring Tajikistan.

Peace talks between the Taliban and the Afghan government remain inconclusive, and many fear the country could descend into a full-blown civil war once again.

Neighbourhoods and markets in the shadow of the base were left ruing the past and bracing for what comes next.

"It is not a problem for us if there are foreign forces (here) or they leave, but the fact that the Taliban are taking over districts at any moment affects our work," Wasim Shirzad, a shopkeeper told Reuters.

Another shopkeeper Nematullah Ferdaws, agreed: "Most shopkeepers do not invest [...] because they are hesitant about the country's future."

Header photo: Afghan army soldiers stand guard after the American military left Bagram air base, in Parwan province north of Kabul, Afghanistan on Monday. — AP