MELBOURNE: Unusual torrential rain in Australia's outback turned the Uluru monolith into a series of cascading waterfalls and triggered flash floods, and seven people are missing including a Japanese tourist who was swept away in a car and an Australian family.

Police were using helicopters to search for the family of six, missing since Christmas Day downpours drenched the desert that is usually sweltering in the midst of the southern summer at this time of year.

A car carrying three people, believed to be Japanese tourists, was washed off a road into a flooded creek near the town of Alice Springs, police said.

Two people managed to get out but police had "grave concerns" for the third who was trapped as the vehicle was washed away, said Acting Superintendent Brendan Muldoon.

"We're told by witnesses it rolled over a couple of times and was wedged up against a tree," Muldoon told reporters on Tuesday.

Authorities closed the Uluru-Kata Tjuta National Park, which surrounds the landmark also known as Ayers Rock, as record-breaking summer rain fell on Sunday and Monday.

The rock, a sacred aboriginal site, was shrouded in cloud as water cascaded off it.

Northern Territory Bureau of Meteorology senior forecaster Sally Cutter said more than 232 millimetres (nine inches) of rain fell on the town of Kintore on Monday, more than double the record December rainfall of 110 millimetres (four inches) in 2003.

Uluru is one of Australia's major tourist destinations, attracting 300,000 visitors a year.

The park reopened on Tuesday.

About 80 people remained in evacuation centres in Kintore on Tuesday and roads in the area were inaccessible, a Northern Territory Police and Emergency Service's spokesman told Reuters.