A car bomb exploded outside a bank in Lashkar Gah, capital of the southern Afghan province of Helmand on Thursday, killing and wounding dozens of civilians and members of the security forces waiting to collect their pay, officials said.

Omar Zwak, spokesman for the provincial governor, said at least 34 people had been killed and more than 60 wounded, including members of the police and army, civilians and staff of the New Kabul Bank branch where the attack took place.

There was no immediate claim of responsibility for the attack but insurgent groups, including the Taliban, have in the past targeted banks where police, soldiers and other government employees collect their pay.

Security is worsening across Afghanistan almost three years after international troops ended their main combat mission.

Emergency workers and passers-by tried to help the injured, who were strewn among the dead. Ambulances and private cars ferried the victims to hospitals.

The blast, which also damaged nearby shops, came as Afghans were preparing to celebrate next week's Eid al-Fitr festival marking the end of the holy month of Ramadan.

While high-profile attacks in the capital, Kabul, have made headlines, dozens of similar incidents in provincial centres over recent months have steadily undermined confidence in President Ashraf Ghani's divided government.

Helmand, one of the world's major opium growing centres and a traditional heartland of the Taliban, has been under particularly heavy pressure with large parts of the province in the hands of the insurgents