SYDNEY (AFP) - A man pleaded guilty on Tuesday (July 31) to killing a young mother and her toddler, whose skeleton was found in a suitcase on the side of a road, ending a case that baffled police and shocked Australians.

Daniel James Holdom, 43, admitted the double murder in 2008 of Karlie Jade Pearce-Stevenson, then aged 20, and her two-year-old daughter Khandalyce Kiara Pearce, when he appeared in the New South Wales state Supreme Court.

Pearce-Stevenson's bones were discovered in 2010 in Belanglo State Forest in New South Wales, notorious as the site where seven backpackers' bodies were dumped during a serial killer spree in the 1990s.

Police were unable to identify her until 2015, when her child's remains were found by a passer-by in a suitcase near a highway close to a small South Australia town about 1,100km away.

The child's discovery prompted two calls to a police hotline that eventually helped investigators identify the pair through DNA.

Holdom, who had a short relationship with Pearce-Stevenson, allegedly stamped on her throat and crushed her windpipe before leaving her body in the forest, Sydney's Daily Telegraph reported, citing court documents.

A few days later, Holdom claimed he was driving her daughter to South Australia to her grandmother's house. But he killed her, placed her body in a suitcase and dumped it alongside the highway.

Police also alleged he kept photos of Pearce-Stevenson's body as a "trophy".

Holdom will be sentenced in late September.