Hosea Yemo and Ismael Alua of the West Papua National Committee (KNPB), which organized the rally involving 405 protesters in several cities in Papua including Merauke and Wamena, were detained for allegedly committing treason and provoking other participants of the rally to commit treason.

(Read also: Accused of treason, dozens of Papuan arrested in Manado)

Article 107 of the Criminal Code on treason carries a maximum sentence of 15 years in prison.

"It was a peaceful rally held to demand justice regarding Trikora [Three People's Command], but the police reacted repressively," said Gustaf Kawer, the lawyer of the two activists.

Gustaf was referring to an act on Dec. 19, 1961, when Indonesia then president Sukarno issued a decree on the establishment of the Trikora military operation in order to annex Papua, which was later called Irian Jaya.

"If people want to express their opinion through a rally, the police should escort them. But we have always faced oppression here in Papua," he said.

The KNPB has been fighting for the self-determination of West Papua, which comprises Papua and West Papua provinces, an action that the government considers to be treasonous and an act of separatism because of their call for independence.

On Monday, rallies were held in Jayapura, Merauke, Nabire, Yogyakarta, Manado, Wamena, Jakarta, Sorong, Manokwari, Timika, Yahukimo, Bandung, Ternate and Ambon.

In total, 528 people were arrested Monday and although many were later released, some like Hosea and Ismael were detained. (fac/evi)