Five children have been evacuated from offshore detention in Nauru as Australian teachers prepare to strike on Universal Children's Day.
Seventeen children remain in the centre.
About 250 refugee children have been evacuated from Nauru since 2012.
The Asylum Seeker Resource Centre said the children were being transferred for medical treatment for critical health conditions caused by their prolonged detention.
Meanwhile, hundreds of Australian teachers are expected to walk off the job this afternoon to protest the detention of refugees on Nauru and Papua New Guinea's Manus Island.
Rallies are being staged in Melbourne, Brisbane and Sydney to coincide with Universal Children's Day.