Four child refugees released to live in the community in Nauru say they were physically assaulted on Sunday night, and threatened with death if they stayed on the island.

The boys – aged between 15 and 17 and without parents on Nauru – have told Guardian Australia they were stopped by a group of Nauruan men on motorbikes as they walked home in the evening.

“They said ‘who are you?’. We said ‘we are UAM [unaccompanied minor] refugees’,” one of the boys said. “They started swearing, they said ‘all mother-fucker refugees, we will kill you, this is our country and no one can protect you, not even Save the Children or immigration’.

“Then they started hitting us by punching, kicking, and they [kept] threatening [us] and swearing.”

One of the boys was left unconscious during the attack.

Two of the boys escaped to a nearby beach where they hid behind a rock and used a mobile phone to call Save the Children staff, who act as carers for the child refugees without parents.

Nauru police were alerted, and Save the Children workers were able to find all four boys, who were taken to hospital.

One boy, who had been struck repeatedly on the neck and head, was held overnight for observation.

The other boys suffered bruises, scratches and one, a bite mark.

Injuries to an unaccompanied child refugee on Nauru. Photograph: Supplied

Attacks on refugees on Nauru have escalated in recent weeks. Young men and teenage boys are allegedly particular targets.

Also on Sunday night, sources told Guardian Australia a 15-year-old boy was attacked inside a refugee camp by a group of men, who punched him and repeatedly hit him with a stick.

Twenty-nine child refugees without parents were released from detention at the start of this month to live in the community in Nauru.

They were released because of daily protests in the Australian government-run camps, and escalating rates of self-harm among children.

The children released are recognised by the Australian government as refugees. They cannot be returned to their homeland because they face persecution.

When they were removed from Australia the immigration minister, Scott Morrison, transferred guardianship of the children to the Nauruan minister for justice.

Most of the children are housed in a single large home near Yaren, the largest town on Nauru.

The children’s location is known to the Nauruan community, and some child refugees have reported being accosted and attacked inside their house.

Others have stopped going to school for fear of being attacked while they walk.

The teenagers say they have been told not to fight back if Nauruans attack them. Photograph: Supplied

“We are feeling unsafe, the people … are trying to harm us, specially UAMs,” one of the boys told Guardian Australia. “No one can protect us from these local people, they are very dangerous and they threaten to kill us. We [are] all afraid of them. Save The Children and immigration are not able to protect [us], even they are confessing that.”

He said they had been warned by senior members of the Nauruan community not to fight back. “They will not kill you, just hit you. And don’t try to resistance [sic], the local people are like a family.”

Save the Children told Guardian Australia that Nauru, a small, remote island with a small population and limited resources, was not a suitable place for refugee children, particularly those without family, to live.

“Save the Children is appalled by any instance of assault on refugee children in Nauru,” a spokeswoman said. “Unaccompanied child refugees are some of the most vulnerable – far from home, family and friends, many already witness to horrors no child should go through. These children deserve every protection that can be offered.”

ChilOut founder Dianne Hiles said some of the boys had been in detention 14 months, and had witnessed acts of self-harm by other refugees and asylum seekers. They were being further traumatised by the attacks on them.

“No child should live like this,” she said. “The boys have been stripped of hope and dignity as a result of this government’s policies, and now they have been denied the fundamental right to education as a result of near-continuous verbal and physical harassment when they leave the house.”

Nauru police have been contacted for comment, as has Morrison’s office.