At least 10 mine clearers working for Halo Trust in Afghanistan's northern province of Baghlan have already been shot dead, and greater than a dozen wounded.
Afghan officials blamed the Taliban, saying militants "started shooting everyone" found in the compound.
But Halo Trust CEO James Cowan told the BBC that "the neighborhood Taliban... came to our help and scared the assailants away". The Taliban in addition has denied the attack.
Violence has surged while the US commenced to withdraw it has the last troops on 1 May.
The departure of international troops comes amid deadlock in peace talks between your Afghan government and the Taliban.
Several districts in Baghlan province have observed fierce fighting between your Taliban and government forces.
The employees were killed when masked gunmen burst to their compound at 21:50 (17:20 GMT) on Tuesday, once they had spent a working day removing mines from a nearby field.
Interior Ministry spokesman Tareq Arian told reporters that "the Taliban entered a compound of a mine-clearing agency... and began shooting everyone".
However the Taliban issued a swift denial.
"We condemn episodes on the defenceless and view it as brutality," the militant group's spokesman Zabihullah Mujahid tweeted. "We've ordinary relations with NGOs. Our Mujahideen will never perform such brutal attacks."
Mr Cowan of the Halo Trust told BBC Radio 4's Today programme that the attackers went "bed to bed" shooting the personnel "in cold blood" - but that the neighborhood Taliban helped the deminers.
"I think it is important to understand that the Taliban have denied responsibility because of this, and indeed the neighborhood Taliban group found our help and scared the assailants off," he said.