Jonathan Rea has commenced his title defence with victory in the opening race of the World Superbikes Championship at Phillip Island.

Rea beat Chaz Davies in a drag to the line after an enthralling 22-lap battle which saw five different riders take turns leading.

Marco Melandri jumped best from the outside of the front row as Rea dropped from pole to third.

Rea took only a lap to return to his starting position, through Doohan Corner, and his Kawasaki Racing teammate Tom Sykes followed him through.

Melandri, however, reclaimed the lead on his factory Ducati on lap 6, and Sykes relegated the 2015 and 2016 champion Rea to third on lap 10.

Sykes soon led before Alex Lowes, who had been running around the back of the front-running six-bike pack, charged up the order on his factory Yamaha on lap 11.

Rea took the lead off Lowes two laps later and looked set to skip away before Sykes and Davies reeled him in and went past at Doohan Corner on lap 17.

A Lowes lunge at the Turn 4 Hairpin forced Rea and Davies to stand up on lap 18 as he climbed back to second.

That pair returned the favour less than a lap later, before Rea passed teammate Sykes for first on lap 20 and Davies followed.

Davies threw his factory Ducati up the inside of Rea at Doohan Corner on the final lap but could not make the move stick, and ultimately fell just 0.04s short at the line.

The final step on the podium was a similarly close-run thing with Sykes prevailing over Lowes.

Lowes will, however, start Race 2 from first position due to the new-for-2017 grid system that also sees the Race 1 top three relegated to row three.

Melandri retired after a mid-race off, while Australian wildcard Josh Brookes also failed to finish with technical problems on his Yamaha.

In Australian Superbikes, Daniel Falzon won from pole position, with two further races on Sunday.

World Superbikes Race 2 will be run on Sunday from 1500 AEDT.

Results: Race 1