Three landscapers in Binh Duong Province were injured Monday, after one of them accidentally struck a piece of leftover ordnance while cutting grass.
Le Thanh Phong, 33, accidentally set off the explosive device while clearing tall grass around a rubber plantation.
The explosive left a crater in the ground approximately 40 centimeters deep, VnExpress reported on Tuesday.
Police have not identified the device but say it was highly destructive.
The resulting shrapnel pierced deep into Phong and the two women working alongside him. One of the victims was allegedly standing around 100 meters from the explosion.
Last Wednesday, Nguyen Huu Hau, 41, also from the southern province was severely injured while ploughing his rubber plantation and struck a buried explosive item.
Most of unexploded ordnance around the country are left from the Vietnam War.