(CNN) Australian advocates and opposition politicians are campaigning to free 119 children from forced detention on a tiny Pacific Island, amid warnings that the health of several young refugees is quickly deteriorating.

One 12-year-old boy, detained on Nauru under the Australian government's strict border policies, is seriously ill after refusing to eat for at least two weeks and needs to be transferred to the mainland for treatment, doctors say.

Doctors for Refugees President Barri Phatarfod told CNN the 12-year-old boy was one of several young children on Nauru whose health was progressively deteriorating.

"We can only assume (he has) depression because of his progressive withdrawal from different aspects of life ... We know he refuses to eat and refuses to drink," Phatarfod said.

There are 119 children still living on Nauru after being transferred there under Australia's immigration policy, which bans asylum seekers who arrive by boat from being settled on the mainland.

Read More