SAN MARINO - Defending world champion Marc Marquez of Spain on his Honda won an enthralling San Marino MotoGP on Sunday as Yamaha's Valentino Rossi blew his chances with tactical errors and teammate Jorge Lorenzo crashed out.

The decision by the Honda rider to switch to slick tyres on a drying Misano World Circuit Marco Simoncelli, after earlier rain, led to his fourth win of the season in front of British riders Bradley Smith (Yamaha) and Scott Redding (Honda). Redding rode a remarkable race after dumping his bike in the dirt only to get back up and finish third which completed the first time two British riders had finished on the podium since 1979.

"The bike was moving about and I thought it was time to change as the track was drying out and it was new asphalt. It's nice to be here again on the podium and victory was our target so I'm very happy," said Marquez who becomes the first Honda rider to win at San Marino since compatriot Dani Pedrosa in 2010.

Championship leader Rossi and his army of home fans who had come to see the nine-time world champion looked on in bewilderment as he failed to make the switch from wet tyres to slicks with seven laps to go, when he was in the lead, which handed the race to Marquez. The 'Doctor' eventually settled for fifth place but it was still a successful day as Lorenzo's crash means Rossi extended his championship lead to 23 points over his Yamaha teammate with Marquez now 63pts back with five races to go.

Smith, 24, who made the brave decision to stay on slick tyres for much of the race was rewarded with his best ever result in MotoGP. "I went one lap, then two laps (on slicks) but I just kept saying 'luck favours the brave, luck favours the brave, luck favours the brave' and all the others were making two pit stops but I never expected to be on the podium," said the Oxford rider whose best previous finish in the highest category was third in Australia in 2014.

Lorenzo took the early lead with Marquez and Rossi in hot pursuit but just minutes into the race rain began to fall on the freshly laid new track which forced the field to scramble for a switch of bikes and wet tyres. The leading trio came into pit lane together and swiftly hopped onto new bikes but it was Marquez who took advantage and went into the lead as they came back out with 20 laps to go.

With 15 laps to race and the track drying out, Lorenzo and Rossi blew past Marquez as the Spaniard inexplicably looked behind him, much to the delight of the fans who went wild at the sight of the Italian moving into contention for back-to-back wins for the first time since 2009. The two Yamahas then began to pull away from Marquez but Rossi again turned the race upside down with a daring overtake with 12 laps to go as he took the outright lead for the first time.

However, Rossi stayed out on the track too long and with Marquez on faster tyres, he quickly caught the Italian when the Yamaha rider finally came into the pits and relinquished the lead for good. Earlier, Johann Zarco won his sixth race of the Moto2 season on Sunday as Kalex bikes swept the top three places, and gave the Frenchman an extended lead in the championship standings.

Chasing his first world title, the 25-year-old from Cannes drove a brilliant race to take the chequered flag 3.85sec ahead of Spanish teammate Tito Rabat with Japan's Takaaki Nakagami coming third on another Kalex at 5.388sec. Itay's Enea Bastianini on a Honda won the Moto3 race after the the 17-year-old started from pole position at the Misano circuit and he came home ahead of Portugal's Miguel Oliveira (KTM) and another Italian, Niccolo Antonelli, on a Honda.