A Sydney ward of the state with a medical condition has been abducted by his mother and taken to Queensland, police say.
Tamara Jankovic, 29, is alleged to have taken six-year-old Matthew Papalia against court orders from a relative's home in Liverpool in Sydney's west on January 13.
They boarded a plane that evening to Brisbane and then took a bus to Southport in southeast Queensland, police believe.
They believe the pair are still in the Brisbane area or the state's southeast.
Detective Inspector Dean Johnstone said police had to make a public appeal after Jankovic stopped communicating with the family.
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"The family are concerned for Matthew and for Tamara," he said on Tuesday.
"We urge Tamara to come forward to ensure the wellbeing of her son."
Police are worried that she may not be able to provide constant and adequate care for her son's medical needs.
A warrant has been issued for her arrest and she is expected to face charges of child abduction.
Matthew is described as being of Caucasian appearance, between 105cm and 110cm tall, with a thin build and fair complexion.
He has brown hair and brown eyes.
His mother is described as being of Caucasian appearance, between 170cm and 175cm tall, with medium build and a fair complexion.
She has blonde hair and blue eyes although police believe she may have changed some of her appearance.
Detectives are working with the family, Department of Community Services and NSW and Queensland Police to find the pair.
