The Westpac Rescue Helicopter Service (WRHS) was tasked to the Merriwa District Hospital about 4pm.

"The girls, believed to be aged seven and 10, were admitted to the facility with injuries after the quad bike they were riding on rolled," WRHS community liaison officer Graham Nickisson said in a media statement.

"Hospital staff and the WRHS critical care medical team stabilised them.

"They were then transported to Newcastle, each in a stable condition - the younger girl with a possible broken arm and the older one with minor injuries."