The United Nations' demining officials in Afghanistan on Wednesday in a statement strongly condemned an attack in which unknown militants shot dead four deminers in southern Helmand province.

The statement said that another deminer is reported missing in the province.

"The Mine Action Programme of Afghanistan (MAPA) will not be deterred from this important work by such attacks, which violate the most basic principles of humanity," the UN Mine Action Service (UNMAS) said in a statement.

MAPA provides employment to over 10,500 Afghan citizens.

"There is no known motive for the unprovoked killing of these humanitarian workers," UNMAS added of the attack, which took place in Abbazhai village of Nahr-e Seraj district as demining teams were conducting normal mine clearance activities.

The local officials of Helmand said that the attack took place at about 11 am local time after a number of Taliban insurgents attacked the deminers in Greshk district of the province while the deminers were at work.

However, the officials did not provide further details about the attack.

The Taliban has not yet commented on the attack.