JAKARTA, Indonesia — Human rights lawyers said Thursday they were mounting a court challenge to Indonesia's detention of three Papuan activists on charges of treason.

The lawyers said 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, in December and acted unlawfully in charging activists with treason.

In a statement, the lawyers said they were also demanding police publish apologies to the West Papua National Committee in the media for three consecutive days and pay damages of 126 million rupiah ($9,000).

Amnesty International has called for police to drop the charges and release Yanto Awerkion, Sem Asso, and Edo Dogopia.

It said 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.

Separately, a globe-trotting Polish citizen, Jakub Skrzypski, is on trial in Indonesia on charges of fomenting rebellion after meeting with Papuan activists in August and allegedly communicating with separatist rebels. He faces up to 20 years in prison if convicted.

An armed insurgency has simmered in the Papua region since Indonesia took control of it from the Netherlands in the early 1960s.