Republic of Congo police say security forces have killed 15 rebel fighters during an operation in the Pool region that has been plagued by violence since last year.
Police on Saturday said the Ninja militia members had been trained in explosives and were preparing to commit a series of attacks along the railway between Pool and the capital, Brazzaville.
Police say they seized weapons and ammunition in Madzia, about 53 kilometers south of Brazzaville.
Ninjas Nsiloulou fighters began launching attacks in April 2016, just weeks after President Denis Sassou N'Guesso's re-election.
An arrest warrant is out for Frederic Bitsangou, a pastor who led the group until it disbanded in 2003. He has been missing since April, but through a spokesman in October called for a political solution to hostilities.