Omar Zwak, the Helmand governor's spokesman who gave the casualty figures, said the attack occurred in a market in Nawa, a district in the centre of the province, which has seen heavy fighting in recent weeks as government forces have battled for control with Taliban insurgents.
Afghan forces said they had retaken Nawa district in July but there has been continued fighting in the area since.
Afghanistan's Shias call for protection after latest mosque attack
There was no claim of responsibility and no immediate comment from the Taliban, which has carried out regular suicide attacks in Helmand, where it controls much of the area outside the provincial capital Lashkar Gah.
The hospital in Lashkar Gah run by the Italian aid group Emergency said it had received 3 dead and 19 wounded while Bost Hospital, another facility, said it had received 10 wounded.
It was unclear whether any of the wounded had died after being taken to the hospitals.
Suicide bomber kills NATO soldier in Afghanistan: official
The attack comes just days after a suicide bomber in Lashkar Gah killed at least seven people and wounded 40 as the Taliban continued its push to restore strict Islamic rule to Afghanistan and drive out foreign forces backing the government in Kabul.
US President Donald Trump last week announced a stepped-up military campaign against Taliban insurgents who have gained ground steadily in Afghanistan since a Nato-led coalition ended its main combat mission in 2014.
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