Some 60 people were also wounded in the assault on a bank in the provincial capital as civilians and members of the security forces were queuing to withdraw their salaries.
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.
At least 34 people had been killed and around 60 wounded in the attack, Omar Zwak, spokesman for the provincial governor, told TRT World.
Video from the scene showed victims of the blast arriving at the Emergency Surgical Centre in Lashkar Gah.
Those killed are thought to include members of the police and army, civilians, and staff of the New Kabul Bank branch where the attack took place.
The attack took place "within four hundred to five hundred metres [yards] of the governor's office," Zwak told TRT World.
The attack happened as civilians, police, soldiers and other government employees flocked to the bank to collect their pay, a few days before Eid al Fitr, the festival that marks the end of the Muslim holy month of Ramadan.
There was no immediate claim of responsibility but insurgent groups, including the Taliban and Daesh, have in the past targeted banks.
A heavily contested area
For years Helmand province was at the centre of Western military intervention in Afghanistan. But it has recently slipped deeper into a quagmire of instability.
Insurgents control vast swathes of the province, which is a base for opium production, and have repeatedly threatened to seize Lashkar Gah.
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.
Intensified fighting last year forced thousands of people to flee to Lashkar Gah from neighbouring districts.
Since they launched their spring offensive in late April, the Taliban have been mounting lethal assaults on the Afghan army and police outposts in Helmand.
Boots on the ground
Washington is soon expected to announce an increase in the US military deployment to bolster Afghan forces as they struggle to contain the insurgency. American military commanders in Afghanistan have requested thousands of extra boots on the ground.
US troops in Afghanistan now number about 8,400, and there are another 5,000 from NATO allies, a far cry from the US presence of more than 100,000 six years ago. They mainly serve as trainers and advisers.
Pentagon chief Jim Mattis this month acknowledged that America still is "not winning" in Afghanistan, nearly 16 years after the US-led invasion toppled the Taliban regime.
Producer: Azaera Amza