Indonesian police say they have arrested three suspected Islamic militants thought to be planning terror attacks, including the nephew of a radical cleric imprisoned on terror charges.

Police spokesman Brig. Gen. Boy Rafli Amar says Samidi, an alleged instructor at a jihadist military-camp on Sulawesi island, was arrested Tuesday in Central Java's Purwokerto town.

Hours later, suspected bomb maker Slamet Pilih Utomo was arrested in Solo, the hometown of radical cleric Abu Bakar Bashir.

Amar said Wednesday that those arrests led police to Bashir's nephew, Qomasu Muawiyah Arob, who uses the alias Nuaim.

Police believe the men were planning terror attacks targeting police or an elite anti-terrorism squad.

Since January, Indonesian police have arrested about more than 30 militant suspects and killed 18 in a series of raids.