Authorities are ramping up security patrols around Nauru's key buildings and infrastructure ahead of expected refugee protests.
Refugee Action Coalition spokesman Ian Rintoul says a major protest is planned for Friday.
Mr Rintoul says the protest will be peaceful but refugees want to show their disgust at "being treated like slaves" by the Nauru and Australian governments.
The Nauru government is increasing police and private security guard presence at the power station, fuel depot, airport, hospital, government buildings, parliament, court house, harbour and ports, phosphate mines and other buildings.
In a notice distributed publicly, the government warned would-be trespassers that unauthorised access to designated areas will result in criminal charges and could attract fines of up to $10,000 or one year in jail.
Nauru photographer Clint Deidenang told AAP there was growing tension on the island between locals and refugees.
"The police are on high alert," he said.
"Locals are not happy with what the (refugees) have been given."
Mr Deidenang said there were reports circulating on the island that refugees had been gathering materials for improvised weapons.
Hundreds of refugees, now living in the community, have stopped co-operating with the Nauru government and Australian immigration department.
Mr Rintoul said refugee children were boycotting school and English classes.
Refugees are also refusing to talk to their case managers.
Many with jobs, including public service positions, have quit or are on strike.
