The four PREPAK-P militants were arrested during a search operation, they said on Monday.
The militants were identified as Henry Meitei, Peter Singh, Naoton and Ibungo Singh.
Weapons including one AK 47, nine rounds of ammunition, one pistol, three Chinese-made hand grenades and other explosive materials were recovered from their possession.
The four have been handed over to Imphal west district police station for further interrogation, they said.
The militants were planning to plant bombs and other explosive materials at many places to attack security personnel, police added.