The region's president and police chief have called for people not to take the law into their own hands.
New Dawn FM reported dozens of houses were burnt and police cars stoned following the killing of a man on Sohano Island on Friday night.
Sebastin Siperau is reported to have died in a confrontation over money.
Police reported his relatives and friends then attacked a compound on Sohano and burnt 34 houses in the early hours of Saturday.
There were also reports some relatives went to the main town of Buka, to avenge the death.