CRPF and District Voluntary Force (DVF) stumbled upon the landmines during a joint combing operation in the forests near Siriguda, Naxal Operation Cell sources said.
Two of the landmines weighed 20 kg each while the other one was about 10 kg, the sources said, adding, the bomb disposal squad of the police defused them.
Besides the three landmines, four detonators, banners and posters were found hidden in a pit covered with dry leaves and wooden planks inside the forest.