The mother vanished after the pair allegedly arranged to meet to discuss borrowing money.

A desperate search is underway for the body of a mother who was allegedly kidnapped and murdered by her estranged son.

Sandra Popovic, 58, was last heard from about 4.50pm on Monday when she told family she was meeting her estranged son, Ante Ivan Popovic, at John Curtin Reserve in Winston Hills in Sydney’s northwest.

When she failed to return home and relatives were unable to contact her, police launched an investigation.

Sandra’s car was found on Dodson Crescent about 9.30am on Tuesday.

Ante, 33, was arrested about 1.40pm on Thursday while sitting in a white Toyota Hilux in bushland along Parnell Fire Trail at Tomerong, about 20km south of Nowra.

He was charged with murder and refused bail when he appeared before court on Friday.

He is due to face court again on August 12.

CCTV footage appears to show Ante’s white Toyota Hilux circling streets in the area shortly after 4pm on Monday, before Sandra arrived about 5.10pm.

Superintendent Barry Vincent said the pair had arranged to meet to discuss borrowing money.

He said communications directed towards Sandra before the meeting were “hostile in nature”.

Police allege Sandra’s phone was in Ante’s possession when he drove west into regional NSW about 5.14pm, and that she was not with him when he later returned.

“Following the investigation today, we were satisfied that there was sufficient evidence for us to put the matter before the court,” Vincent said, explaining why police proceeded with a murder charge before Sandra’s body had been located.

He said investigators had obtained forensic evidence as part of the inquiry.

Detectives have tracked the son’s ute to areas out west, beyond the Blue Mountains, and that’s where they’re searching for a body.

Vincent described Sandra as a mother of several children and said Ante had been estranged from her.

He added that Ante was well known to officers.

Sandra’s devastated family is appealing for anyone with information to come forward.

Police are particularly urging residents in Winston Hills, especially those living near John Curtin Reserve on Dodson Crescent, to review any CCTV or dashcam footage captured between 4.30pm and 6pm on Monday.

Anyone who saw a white Toyota Hilux dual-cab ute in the area during that time is urged to contact Crime Stoppers.

Detectives were back at the Winston Hills Park on Friday afternoon walking a potential witness through Monday’s crime scene.

The search for Sandra’s body continues on Friday night with police facing an enormous task of scouring huge tracts of bushland.

They’ve so far traced her son’s mobile phone to a tower near Hartley, a small village outside of Lithgow, but beyond that, nothing.