U.S. soldiers inspect the site of suicide car bombing in Kabul, Afghanistan, May 17, 2015.(Photo: Xinhua)

The US military will hand over its main Bagram Air Base to Afghan forces in about 20 days, an official said Tuesday, as Washington carries out its final withdrawal after nearly two decades of war.

The vast base, built by the Soviets in the 1980s, is the biggest military facility used by US and NATO forces in Afghanistan, with tens of thousands of troops stationed there during the peak of America's military involvement in the violence-wracked country.

"I can confirm we will hand over Bagram Air Base," a US defense official told AFP.

An Afghan security official said the handover was expected in about 20 days, and the defense ministry had set up special committees to manage it.

In Washington, the Pentagon indicated that the pace of the withdrawal was picking up. As of Monday, US Central Command estimated it had completed 30-44 percent of the so-called "retrograde" process. It has shipped the equivalent of 300 loaded C-17 transport planes out of the country.

In April, President Joe Biden set a target of September to remove all the 2,500 US troops and some 16,000 civilian contractors out of the country, aiming to end the US military's two-decade-old presence.

Bagram base was the center for nationwide command and air operations for the past two decades.

It also houses a prison that held thousands of Taliban and jihadist inmates over the years.

Washington had already handed over six military bases to Afghan forces before May 1, when it began accelerating the final withdrawal of troops.

In May, it completed the withdrawal from Kandahar Airfield in southern Afghanistan, once the second-largest foreign military base in the country.

The US withdrawal comes despite bloody clashes across the country between the Taliban and Afghan forces.

In the latest violence to rock the capital Kabul, at least 10 civilians were killed and 12 wounded in two separate blasts targeting passenger buses in the city late on Tuesday, police said.

In a separate incident, an explosion caused a power outage leaving several parts of Kabul in darkness.

AFP