According to the local officials, the incident took place at around 9 am in Malang Kariz area of Maiwand district.
Zia Durrani, spokesman for the provincial police chief said the deminers were shot dead by militants while they were clearing the path for the TAPI gas pipeline project.
He added that the sixth worker is missing and his fate is unknown.
The official claimed that the de-miners had told security officials no threat was posing against them from the Taliban insurgent group and there was no need for security measures.
Security officials have blamed Taliban for the shooting incident, adding their investigations are underway.
The Taliban militant group have not claimed responsibility for the attack.