Afghanistan's defence minister and army chief of staff have resigned in the wake of a Taliban attack that left scores of soldiers dead, the presidential palace says.

The attack happened on Friday at an army base near Mazar-e Sharif.

Insurgents targeted troops leaving Friday prayers at the base's mosque and in a canteen, the army said.

It was the Taliban's deadliest attack on the armed forces since US-led forces drove them from power in 2001.

The resignations coincided with the arrival of US Defence Secretary Jim Mattis on an unannounced visit to Kabul. He is due to meet both Afghan officials and US troops.

Insurgents are also reported to have attacked a base in Khost, in eastern Afghanistan on Monday. A car bomb detonated at the entrance to Camp Chapman, a US-operated base, and there were a number of Afghan casualties, Reuters news agency reported.

How did the Mazar-e Sharif attack unfold?

A group of about 10 Taliban insurgents dressed in Afghan military uniforms and driving military vehicles made their way into the base in the northern city and opened fire.

Many of those who died were young recruits training at the base. Witnesses described chaotic scenes as the young soldiers struggled to work out who was friend or foe.

The attackers were armed with guns, grenades and some were wearing suicide vests, reports said. The defence ministry said the attackers were all killed.

It is not clear exactly how many soldiers died. The Afghan defence ministry has not released firm casualty figures, only saying more than 100 people were killed or injured.

Other officials have told BBC that at least 136 people died - 124 coffins had been sent out to different parts of the country and 12 soldiers had not yet been identified, they said.

But some sources say the toll was even higher. One eyewitness told the BBC he counted 165 bodies.