The Taliban attacked three checkpoints in the western Farah province of Afghanistan, killing at least six policemen, an Afghan official said on Sunday.

Mohammad Naser Mehri, a spokesman for the provincial governor, said eight other policemen were wounded in the late Saturday attack. He claimed eight insurgents were killed and at least five others were wounded in the battle.

The Taliban claimed responsibility for the attack.

Elsewhere in Afghanistan, seven militants were killed and two others wounded when a bomb exploded prematurely in the northern Kunduz province. Mahbobullah Sayedi, a district chief, said the fighters died while trying to plant the bomb on a road used by Afghan security forces.

Dozens of Afghan police and soldiers have been killed in a wave of Taliban attacks on checkpoints in Afghanistan, officials had said on Tuesday, as insurgents step up assaults on the beleaguered security forces.

Afghan security forces have faced soaring casualties in their attempts to hold back the insurgents since Nato combat forces pulled out of the country at the end of 2014.

Casualties leapt by 35 per cent in 2016, with 6,800 soldiers and police killed, according to US watchdog SIGAR.

The insurgents have carried out more complex attacks against security forces in 2017, with SIGAR describing troop casualties in the early part of the year as “shockingly high”.

In August, Trump announced that American forces would stay in Afghanistan indefinitely, increasing attacks on militants and deploying more troops.