Jakarta – Indonesian police have released eight activists detained earlier this month in war-torn Aceh province but plan to charge two others with treason for allegedly helping separatist rebels, officials said on Saturday.

The 10 were detained between February 21 and February 25. Their arrest prompted Amnesty International to issue a statement warning that the activists could be tortured and appealing for their release.

Col. Sayed Husaini said the eight were released on Friday for lack of evidence. But he said the two others – Herlina of the Acehnese Democratic Women's Organization and Iwan Irama Putra of the Linge Students Network – will be charged with treason.

"We strongly suspect these two provided refuge for rebels and took part in an ambush by rebels which left three policemen dead," Husaini said.

Indonesia declared martial law in Aceh in May and then launched a large-scale military offensive aimed at defeating the separatist insurgency.

More than 1,500 people – many of them allegedly rebels and rebel sympathizers – have been killed since the offensive was launched. Rebels insist most of those killed were civilians and both sides have been accused of murdering and intimidating rights activists.

The Free Aceh Movement has fought for independence of the oil-and gas-rich province on the northern tip of Sumatra since 1976.