The 24-year-old Italian, who started seventh on the grid, produced a perfect display of controlled aggression to take the lead from Sete Gibernau with eight laps to go and win by 9.699 seconds on his Fortuna Honda.

Melandri’s fifth win of his top-level career also made him the first rider to win at Phillip Island in the 125cc, 250cc and Moto GP classes and closed him to just 32 points behind championship leader Nicky Hayden.

Rain on the formation lap forced event officials to declare a wet race after the original start was aborted to give riders a chance to switch to their wet-weather bikes.

As it turned out, nobody did as the rain eased off, and from the re-start, front-row qualifier Shinya Nakano made a tremendous start to assume the lead which he extended to as much as five seconds before the rain – and the pit-stops – began.

Japanese rider Nakano stayed out a lap longer than most and could barely touch the throttle while still on a Kawasaki set up for cry conditions. It was enough to let Spaniard Gibernau into the lead on his Ducati after starting 12th.

Gibernau, a renowned rain-master, looked under control during the wet section of the race as Nakano steadily dropped down to finish an eventual eighth.

Chris Vermeulen, 24, was not going to let Gibernau have the race to himself though, and the Australian Suzuki rider – who endured the worst qualifying session of his career on Saturday – began to close in.

The key was the Bridgestone tyres that both Ducati and Suzuki were running, but home fans, remembering Vermeulen’s wet pole position in Turkey, began to think that a first home win since Mick Doohan in 1998 could be possible.

The problem for the front pair though, was that as the rain stopped and a dry line emerged, the advantage swung towards the Michelin-tyred contingent.

The first of these was Melandri, who swept past Vermeulen at the final corner on lap 17 and then dived inside Gibernau before riding into the distance.

Vermeulen passed Gibernau almost immediately and managed to hold on to second to claim his first podium finish. The Spaniard, however, was not so lucky.

After a disastrous start that dropped him to 11th on lap one, Italian Valentino Rossi spent the race carving through the field on his Yamaha.

The five-time world champion’s Michelins came alive at the end of the race and he was able to go from seventh to third in four laps - snatching the final podium spot from his old rival Gibernau at the final corner of the race.

In doing so, he shaved five points off Nicky Hayden’s championship lead to lie 21 points behind the Repsol Honda rider with three races left and 75 points still up for grabs.

American Hayden, 24, could only finish sfifth - ahead of Australian Casey Stoner on an LCR Honda - after a terrible start, that dropped him from pole position to 16th on the first lap, left him on a determined fightback.

Seventh was Italian Loris Capirossi on a Ducati ahead of Nakano, Melandri’s Spanish team-mate Toni Elias, and Japanese Makoto Tamada on a Konica Minolta Honda.

Frenchman Randy de Puniet - who was quickest on the first day of practice - took the best finish of his Moto GP career in 11th for Kawasaki, while Spaniard Dani Pedrosa could only manage 15th on his Repsol Honda and dropped to fourth in the points.

Eurosport