Election related mayhem and a gun attack on a crowded minibus killed 21 people in Indonesia's restive Papua region, police said Monday. The unrelated incidents come ahead of local elections and amid a low-intensity insurgency against Indonesian rule by poorly armed indigenous militias. In the bloodiest violence, clashes between hundreds of supporters of rival election candidates killed 17 people and injured dozens in remote Puncak district on Sunday, police said. Armed with machetes, rocks and arrows, mobs of people torched houses and cars during the mayhem, local police chief Alex Korwa said. "We've deployed dozens of police and military to secure the area. The situation is tense but under control," he said, adding that investigations were ongoing. The recently created district, which is only accessible by plane, is scheduled to hold its first local elections on November 9. In a separate incident, unknown gunmen shot dead four people including a soldier and wounded at least seven others in an attack on a minibus in Abepura district on Monday, police said. The attackers blocked a road near Nafri village and opened fire at the passengers inside the bus, Papua provincial police spokesman Wachyono told reporters. "Four people, including a military officer, were shot dead. At least seven others were injured after being attacked with sharp weapons, possibly axes and machetes," he added. "We're still investigating the group's identity, what weapons they had used and what their motive was." The investigation would consider whether the gunmen were from the Free Papua Movement (OPM) rebel militia, he added. The OPM has waged a low-level insurgency -- often using bows and arrows rather than guns -- against Indonesian rule of the resource-rich, ethnically Melanesian region since 1964.