National police chief Ismail Omar said the suspects’ actions “could have threatened national security.” He did not elaborate and other police officials declined to comment.

Six of those arrested in eastern Sabah state this week are foreigners. Ismail did not reveal their nationalities.

Sabah borders the restive southern Philippines and Indonesia’s Kalimantan province in Borneo.

Rights group Suaram said earlier Thursday the suspects include businessmen and two schoolteachers held under the Internal Security Act. The law has been used over the past decade to detain more than 100 militant suspects without trial.