A suicide bomber drove an explosives-packed Humvee into a police compound in Afghanistan Friday, killing at least six officers and destroying a building, officials said.

The Taliban claimed responsibility for the pre-dawn attack on the Maiwand district police headquarters in the southern province of Kandahar, the latest deadly assault by the insurgents, who have been increasingly targeting security installations.

The vehicle was carrying an estimated 3,000 kilogrammes (6,600 pounds) of explosives, Maiwand district police chief Sultan Mohammad told AFP.

It was not possible to verify his claim. If true, that would be roughly twice the number of explosives used in a massive truck bomb in Kabul that killed around 150 people in May.

"We have six police officers martyred and five wounded," Mohammad said, adding the figures could change.

Kandahar police spokesman Ghorzang Afridi confirmed the death toll.

"All the victims were local policemen," Afridi told AFP.

Those killed were new recruits.

While Afghan officials routinely understate the casualty toll in attacks carried out by insurgents, it appears the attacker failed to reach the building where a large number of police were deployed.

Mohammad said the attacker got through the first checkpoint and then detonated the vehicle at the second security check after a policeman opened fire.

One building "was completely destroyed and two other buildings next to it were damaged too," he said.

The force of the blast also blew out the windows of shops located two kilometres away, he added.

"The explosion was very loud and you could hear the sound of the blast miles away from the headquarters," a local police officer told AFP on the condition of anonymity.

He put the death toll at eight with nine others wounded.

"The eight policemen who were killed have been removed or pulled out from under the rubble, and there were other policemen who went missing following the attack," the officer said.

The Taliban have stepped up attacks on security installations as they seek to demoralise police and troops, and steal equipment to fuel the 16-year insurgency.

The militants have acquired "dozens" of armoured Humvees and pickup trucks in recent years, officials have said.

Some of those vehicles have been used in suicide attacks on police and military bases with devastating effect -- including one in Kandahar in October that killed more than 40 Afghan soldiers.

Afghan forces, already beset by desertions and corruption, have seen casualties soar to what a US watchdog has described as "shockingly high" levels since NATO forces officially ended their combat mission in 2014 and began a training and support role.

Morale has been further eroded by long-running fears that the militants have insider help -- everything from infiltrators in the ranks to corrupt Afghan forces selling equipment to the Taliban.