A minivan carrying civilian passengers in north-west Afghanistan has been hit by a roadside bomb, leaving at least 11 passengers dead, including three children, an Afghan official said.

The minivan fell into a valley due to the explosion, said Badghis provincial governor Hesamuddin Shams.

He added that rescuers were still searching for bodies in the valley.

No one immediately claimed responsibility for the explosion but the provincial government accuses the Taliban of placing the bomb to target security forces.

Large swathes of war-ravaged Afghanistan are littered with bombs and landmines. Many were planted by insurgents to target government military convoys, but they often kill civilians instead.

The United Nations has repeatedly demanded both government forces and the Taliban take more precautions to protect civilians.

In the first three months of this year, the UN mission in Afghanistan said that 1,783 civilians had been killed or wounded in the country, an increase of 29% on the same period last year.

The violence comes as US peace envoy to Afghanistan Zalmay Khalilzad travelled to the region to start a new series of talks between the Taliban and the government. They were to meet in Kabul and Doha in Qatar to urge the sides to reach a political settlement.

Negotiations between the Taliban and Afghan representatives began last September in Doha and continued earlier this year. But the Taliban announced on April 13 that it would not take part in any conference intended to decide the future of Afghanistan until all foreign troops were gone.

President Joe Biden had announced a day earlier that all US troops would leave Afghanistan by September 11.

In the northern Faryab province, provincial officials said on Sunday that the district of Qaisar had fallen to Taliban fighters after a long fight between the two sides.

Provincial council chief Mohammad Tahir Rahmani told The Associated Press that a provincial police chief was killed in the fighting along with seven other police officers.

Also on Sunday, a police spokesman said a roadside bomb explosion in eastern Kabul targeted a civilian car, wounding three people.