Indonesia ? The head of Southeast Asia’s most feared terrorist group was arrested along with his military chief, police said Friday, claiming a breakthrough in the fight against extremists in the world’s most populous Muslim nation.

Authorities warned, however, that Jemaah Islamiyah – blamed for the 2002 Bali bombings and other attacks – and breakaway factions could still carry out strikes against Western and Christian interests.

Zarkasih, identified for the first time as the group’s overall leader, was captured June 9 on Indonesia’s main island of Java, hours after anti-terror police closed in on militant chief Abu Dujana, said Brig. Gen. Suryadarma Salim.

Like other top Jemaah Islamiyah members, Zarkasih, 45, went by several aliases and underwent military training in Afghanistan in the late 1980s, where he learned bomb-making and arms handling.