The army yesterday said its raid on the armed group's camp was in response to Friday's deadly attack, when gunmen in four speed boats stormed the Joint Task Force (JTF) base in Nembe in southern Bayelsa state, police had said.
Militants in the camp are thought to have been responsible for a separate attack on a community in Degema municipality in neighbouring Rivers state, army spokesman Lieutenant Colonel Isa Ado said in a statement.
Three speed boats, communication gadgets and generators were also recovered from the suspects, some of whom had managed to escape, it added.
The military spokesman declined to say whether the six suspects under arrest had taken part in Friday's attack on the military base in Nembe.
The JTF was set up to fight rampant theft of crude oil and piracy in the Niger Delta. The region is notorious for attacks by oil thieves and kidnappings for ransom, mainly of oil workers.