A 15-year-old girl from Warwick, Australia, is fighting for her life in a Brisbane hospital after she was brutally assaulted by a group of teenagers on Tuesday (10 October) afternoon.

Police have charged two girls in the case, one aged 16 and the other aged 18. The motive behind the assault was still unclear.

The victim is currently in induced coma in a Brisbane hospital, police said. Her condition is still critical as she sustained life-threatening injuries during the assault. She was flown to the Princess Alexandra Hospital in Brisbane from Warwick on Wednesday morning, the Courier Mail reported.

Warwick detective Sergeant Darren Tamblyn alleged that the victim was punched and kicked in the head repeatedly by the group that intercepted her while she was walking home with a friend from a party.

When the assault began, the victim's friend ran off to seek help from another friend who lived nearby, police added.

"The girl's friend had fled to the other friend's home to find help and call for help. When she took flight a shift worker returning to Warwick from Wacol ... stopped to provide first aid and call the police," the sergeant said.

He added that they have charged the 16-year-old Warwick girl with assault occasioning bodily harm and grievous bodily harm. The other teen from Wilsonton has been charged with grievous bodily harm and is due to appear in Warwick Magistrates Court on Wednesday.

Elaborating on the victim's condition, Tamblyn said: "She has now undergone emergency surgery for a brain injury and she remains in an induced coma.

"Her condition will continue to be monitored over the next 72 hours."