SYDNEY - A 3,000-KILOMETRE (1,860-mile) solar car race across Australia's desert heartland began in the northern city of Darwin on Sunday, organisers said.

The cars left Darwin in hot and humid weather at about 8.30 am (7 am Singapore time) on the journey that is expected to end mid-week in the South Australian city of Adelaide.

'We had 32 vehicles start this morning,' Mike Drewer, a spokesman for the World Solar Challenge, told AFP, adding that weather conditions were good for solar cars. 'The first away was Aurora 101 from Australia, having set the fastest speed time trial (of 91.83 kilometres per hour) yesterday.'

It was followed by the Dutch car Nuna5, which posted a time of 85.49 kilometres per hour. The Nuna team has won the last four solar challenge races in 2007, 2005, 2003 and 2001 but had to rebuild its new car before the start of this race after a testing accident in Darwin.

The solar cars race for nine hours each day, stopping at a certain cut-off time each night and camping by the side of the road, wherever they are at that moment.

'We would expect the fastest vehicles are capable of doing, depending on weather conditions, about 800 kilometres per day,' Drewer said. 'The fastest ones could be approaching Adelaide by Wednesday night, Thursday.' -- AFO