Tensions in Papua, where a separatist movement has simmered for decades, have been running high in recent weeks and some Papuans have been calling for a boycott of the election.

The Indonesian elections are a massive exercise in democracy, with more than 170 million eligible voters scattered across an archipelago of some 17,000 islands.

Because of time differences, voting kicked off in Papua and Maluku in the east of Indonesia. Polling stations open in areas such as the resort island of Bali and the capital Jakarta over the next couple of hours.

A polling station in Heram subdistrict in Papua's provincial capital Jayapura had opened and appeared ready although no one was voting and there was no police officer on duty, a Reuters photographer said.

Police opened fire, killing one person, when a crowd attacked a police post in Jayapura with bows and arrows and petrol bombs overnight, Papua Police Chief Bagus Ekodanto said earlier by telephone.

He said a group of unidentified gunmen had also attacked another small police post near the border with Papua New Guinea, and part of the university in Jayapura was also burned.

Elsewhere, four people died and two were critically hurt in violence in Wamena, southwest of Jayapura, he said.

"The gunmen and other groups tried to make the elections fail," Ekodanto said, calling for calm.

In another town, Biak, a fuel tank and 14 houses were burned and one person was killed, the police chief said.

Another polling station in the town of Nabire, west of Jayapura, had also opened but the head of the station said voting might be delayed since only 55 ballot papers had arrived for 576 eligible voters. (Reporting by Oka Barta Daud; Additional reporting by John Pakage in Nabire and Olivia Rondonuwu in Jakarta; Writing by Ed Davies)