A mine had drifted from a mine field near LoC into a farm land following heavy rains in Janghar area of Nowshera tehsil of Rajouri district, a Defence Spokesman said.
Some labourers at the site spotted it and started fiddling with it resulting in the blast, the spokesman said.
While three labourers died, one person suffered injuries and has been hospitalised.
The agriculture land belonging to a villager was in a mined area. It was later de-mined.
The labourers belonged to Bihar and were engaged in agriculture activities in the area, he said.