About 2,000 people have rallied in Jayapura, the capital of Indonesia's Papua province, calling for independence for the remote, resource-rich area in the far east of the country.
Shouting "freedom", some protesters carried banners on Thursday saying "Review the act of no choice in 1969", referring to a disputed vote that led to Papua being formally incorporated into Indonesia.
Papua, which occupies the western half of New Guinea island, was under Dutch colonial rule until 1963, when Indonesia took over.
Jakarta formalised its rule in 1969 in a vote by community leaders which was widely criticised as flawed.
Protest organisers said the march was timed to coincide with a gathering of parliamentarians in London in support of self determination for Papua.
About 10 lorries carrying police sought to block the marchers, although there were no reports of violence.
Separatist groups have stepped up protests in Papua in recent months.
There have also been several small bomb blasts, including at an airport in Papua and near a copper mine run by the local unit of US mining firm Freeport McMoRan Copper & Gold Inc.
Police also arrested five people this week after an unidentified group hoisted a banned separatist flag in front of a local government office.