At least six people were killed Saturday when a Taliban bomber rammed an explosives-laden car into Afghan soldiers who had queued outside a bank in southern Helmand province to collect their salaries, officials said.

Nearly two dozen others, including women and children, were wounded in the explosion in the capital Lashkar Gah, many of them critically.

The Taliban, who control vast swathes of the opium-ravaged province and have repeatedly threatened to seize Lashkar Gah, claimed responsibility for the bombing, calling it revenge for recent US airstrikes in the volatile district of Sangin.

“A suicide car bomber killed six people, including five soldiers, and 21 others were wounded,” Helmand police chief Agha Noor Kentoz told AFP.

Omar Zhwak, the provincial governor's spokesman, confirmed the casualties from the bombing, which upturned military vehicles and left the area strewn with charred debris.

The Italian-run Emergency hospital in Lashkar Gah said it had received at least 12 people, including a woman and a child.

The Taliban ruled out civilian casualties in a statement on their website, claiming that 21 Afghan army soldiers had been killed. The insurgents are known to exaggerate battlefield claims.

The attack comes after the US military this week stepped up airstrikes in Sangin as fierce fighting with the Taliban raised fears that the key district could fall to the insurgents.

Nato on Friday said it was looking into local media reports of nearly a dozen civilian casualties from the strikes.

“While supporting and defending Afghan troops, the US conducted airstrikes in Sangin district,” the coalition said in a statement.

“We're aware of the allegations of civilian casualties, and take every allegation very seriously. We'll work with our Afghan partners to review all related material.” For years Helmand was the centrepiece of the Western military intervention in Afghanistan only for it to slip deeper into a quagmire of instability.

The Taliban effectively control or contest 10 of the 14 districts in Helmand, the deadliest province for British and US troops over the past decade and blighted by a huge opium harvest that helps fund the insurgency.

Lashkar Gah — one of the last government-held enclaves — also risks falling to the Taliban's repeated ferocious assaults. The intensified fighting in the province last year forced thousands of people to flee to Lashkar Gah from neighbouring districts.

The Pentagon said last month it will deploy some 300 US Marines this spring to Helmand.

Nato officially ended its combat mission in December 2014, but the Marines will return to train and advise Afghan soldiers and police officers fighting the Taliban, said US Central Command.

The decision was welcomed by the Afghan government ahead of what is expected to be another fierce spring fighting season.