Eugene Laverty and Marco Melandri shared the race wins as Sylvain Guintoli extended his lead at the top of the Superbike World Championship in Portugal.

French rider Guintoli had entered the weekend with a slender four-point advantage over Britain's Tom Sykes at the top of the standings, but his pair of second-place finishes ensured the Aprilia man now enjoys a 28-point lead over his Kawasaki rival.

It was BMW rider Melandri who took the spoils in race one at the Portimao circuit as he held off a late charge from Guintoli to triumph by just seven thousandths of a second, making it the fourth-closest finish in the series' history.

Laverty, on the second of the Aprilias, had looked the likely winner until an engine failure forced him out, while fellow front-row man Jonathan Rea was another to hit trouble.

Sykes, who had started from pole, eventually claimed third place, with fellow Brit Leon Camier claiming his career-best result in fourth.

Having been hit by misfortune in race one, Laverty made amends with a dominant run to his fourth victory of the season in race two.

Instead it was Sykes who hit trouble. The pole-sitter crashed on the warm-up lap and the damage to his Kawasaki meant a points finish was beyond him.

Race one winner Melandri fell back as his BMW Motorrad Goldbet machine suffered tyre issues, leaving Guintoli to chase home his team-mate, with Rea taking a solid third on an encouraging weekend for Pata Honda.

But the Larne man's team-mate Leon Haslam suffered more difficulties.

Haslam is still recovering from the broken leg he suffered at Assen and his efforts to compensate for the injury saw him retire from race one with numbness in his arms, leaving him unable to start race two.

A disappointed Sykes said: "In race two the fall was my fault because in turn one on my out lap I ran over the kerbstone on the inside.

"The piece of kerbstone looked quite flat but in the last moment I realised it was a big high kerb and it chucked me over the front of the bike. The bike flipped, landed on me and it was a big crash. It hurt my right leg and gave me a headache.

"I feel I have let a few people down but I do not want to be too hard on myself as it is the first mistake I have made for a long time."