According to Helmand police Spokesman Zaman Hamdard, all the victims were from a single family. The family had just left the southern district to Greshk when the bomb hit their car. Two more family members were wounded.
No one has claimed responsibility for the attack so far. However, both the Taliban and the Islamic State militants are active in the province.
On Tuesday, the Taliban had sent a three-member technical team to Kabul to monitor the release of prisoners as part of a peace deal with the US. The deal signed in February calls for the Afghan Government to release of 5,000 Taliban prisoners and for the Taliban to free 1,000 government personnel and Afghan troops they hold captive.