JAKARTA, Indonesia (AP) — Human rights lawyers are mounting a court challenge to Indonesia's detention of three Papuan activists on charges of treason.

The lawyers said Thursday that police in Indonesia's easternmost Papua region had illegally seized the offices of the West Papua National Committee, which advocates for Papuan self-determination, and acted unlawfully in charging activists with treason.

Amnesty International has called for police to drop the charges and release the three men. It says they were charged and detained "solely for exercising their rights to freedom of peaceful assembly and expression."

Security forces have intensified a crackdown on political activists in Papua after separatist rebels killed 19 people in an attack in December.