A four-year-old Australian girl abducted from a campsite 18 days ago was found to be safe and well when police rescued her after a raid on a locked house in a nearby coastal town on Wednesday.

Cleo Smith disappeared from her family's tent when they were camping in a  remote Western Australia bushland last month after which a frantic search on air, sea and ground was launched involving 100 officers and scores of volunteers.

Many feared the search would end in tragedy, but after a night raid on a home in the coastal town of Carnarvon — just a short drive from where she disappeared — police announced the little girl had been found alone, but alive, according to an AFP report from Sydney.

Detective Cameron Blaine, one of the four rescuers, said that after the initial shock he asked the little girl her name three times before receiving her electrifying response: "My name is Cleo."

Police admitted "seasoned detectives" were "openly crying with relief" at the discovery and when Cleo was reunited with her parents at a hospital a short time later, the AFP report said.

Her mother Ellie took to social media to express her relief. "Our family is whole again," she posted on Instagram under a photo of Cleo.

Police later released an image of the beaming youngster on a hospital bed holding an ice pop, waving and smiling.

It is believed the abduction was unplanned and "opportunistic". The suspect was not on a local list of sex offenders and only became a person of interest a day ago.

Police last month had offered Aus$1 million (US$750,000) reward for information leading to Cleo's recovery.