Provincial governor spokesman Omar Zwak told dpa that their minivan was hit by a roadside bomb in the province's Gereshk district.
Another two civilians were wounded in the blast. Zwak added that the casualty figures were initial and could rise.
Provincial councillor Abdul Majid Akhundzada also confirmed the death toll.
According to local officials, Taliban militants control vast territory in the province, including Greshek district.
Government forces only control the capital, Lashkargah, and five other districts, out of a total of 14 districts in the province. The Taliban controls the remaining territory.
Almost daily attacks from the Taliban and Islamic State militants - as well as accidental shelling from pro-government forces - are taking a toll on civilians in the country.
The number of civilian casualties in Afghanistan since 2009 has recently surpassed 100,000, the United Nations' Assistance Mission in Afghanistan, said in a statement late in December.
The US-led international forces have been in the country for almost two decades, following the collapse of the Taliban regime in 2001 as part of NATO missions.
On February 29, Washington signed a deal with the Taliban that paves the way for the gradual withdrawal of the international troops from Afghanistan. In the meantime, it should open the doors for intra-Afghan peace talks in the war-ravaged country.
Another two civilians were wounded in the blast. Zwak added that the casualty figures were initial and could rise.
Provincial councillor Abdul Majid Akhundzada also confirmed the death toll.
According to local officials, Taliban militants control vast territory in the province, including Greshek district.
Government forces only control the capital, Lashkargah, and five other districts, out of a total of 14 districts in the province. The Taliban controls the remaining territory.
Almost daily attacks from the Taliban and Islamic State militants - as well as accidental shelling from pro-government forces - are taking a toll on civilians in the country.
The number of civilian casualties in Afghanistan since 2009 has recently surpassed 100,000, the United Nations' Assistance Mission in Afghanistan, said in a statement late in December.
The US-led international forces have been in the country for almost two decades, following the collapse of the Taliban regime in 2001 as part of NATO missions.
On February 29, Washington signed a deal with the Taliban that paves the way for the gradual withdrawal of the international troops from Afghanistan. In the meantime, it should open the doors for intra-Afghan peace talks in the war-ravaged country.