Noriyuki Haga has clawed back significant ground on Ben Spies in the World Superbike Championship standings after taking an impressive victory at Imola.

Haga put on a feisty performance to win his first race since Kyalami after snatching the lead on lap 18 before easing to a comfortable win over Max Biaggi. Spies, meanwhile, could only manage fourth.

Biaggi had led the majority of the way, the Aprilia rider taking the lead at the start from sixth on the grid, but while he was able to resist pressure from Haga for almost the race's entirety, he couldn't quite do it to the chequered flag.

More significantly, however, Spies was a relatively quiet fourth after never quite getting on terms with the lead fight. Losing 12 points to Haga in the process, his championship advantage is down to six points.

Although fireworks had been expected off the line with the top four riders in the standings all starting on the front row, it was Biaggi that spoiled their intentions from sixth place, the scrap for the inside line into turn one allowing the RSV-4 to sweep around the inside and grab the advantage.

He headed up pole sitter Michel Fabrizio, Jonathan Rea and Haga, while Spies was getting baulked into the first corner after banging panels with Troy Corser's BMW before recovering for fifth.

With the jump on Spies, Haga wasted no time in moving towards the front, passing Nurburgring sparring partner Rea at the final corner chicane on lap one before putting a bold move on his team-mate at the Variante Alta, Fabrizio seemingly not expecting to see his fellow Ducati rider pass there as he sat up.

Rea's victory challenge, however, would end on lap three when he got out of shape over the crest leading down to the Rivazza complex and being force to straighten up on the tight inside line. With little chance to stop, he careened across the bow of Fabrizio and Haga, the Japanese rider paying enough attention to back off and allow the Ten Kate Honda rider to carry on off into the gravel trap. Forced to lay the bike down, Rea got going again, albeit in last place.

Reducing the group of five down to four initially, the lead pack became three when Spies began to lose ground on the front runners. Seemingly unable to maintain pace, the American was almost three seconds behind after just five laps.