Over 150 Afghan troops have been killed or injured in the last 24 hours in a surge of attacks by Taliban militants as foreign forces withdraw, senior government officials said on Monday.

Fighting is now raging in 26 of the country's 34 provinces, the officials said, speaking on condition of anonymity. Casualties were "shockingly high", one added.

The government says clashes over territory have increased as the United States pushes on with an operation to withdraw all its remaining troops by September 11.

The Taliban seized Shahrak district of western Ghor province on Monday and forced Afghan troops to retreat to nearby villages after a heavy firefight, local officials said.

A powerful car bomb targeting a police headquarters in the Khas Balkh district of Balkh province killed at least four people and wounded 50 more including civilians on Sunday, officials said.

Government troops have launched an operation to recapture a strategic district of Nerkh of Wardak province that lies less than an hour's drive from the capital Kabul, a defence ministry official said.

On the same day, Taliban fighters stormed the Qaisar district of northern Faryab province, killing and wounding dozens of Afghan security forces, a police official said.

"In the past 24 hours, there were unfortunately 157 casualties among forces," one senior official said on condition of anonymity because they were not allowed to speak to media.

Political talks between the government and the Taliban have largely stalled as Washington pulls its troops out 20 years after US bombing forced the Taliban from power.

Both sides have accused the other of provoking and failing to halt attacks against civilians.