Mugello - Italy's Andrea Dovizioso set a new MotoGP speed record but compatriot Andrea Iannone topped Friday's two practice sessions in a drama-filled first day's action ahead of the Italian Grand Prix at Mugello.

Ducati's Dovizioso posted a new top speed record of 356.4km/h (221.5mph) to better the previous best of 354.9km/h achieved by Iannone in 2016. 

But the 28-year-old Iannone, who has confirmed he will leave Japanese manufacturer Suzuki at the end of the season, achieved a combined time of 1min 46.735sec after the two sessions.

Yamaha's Maverick Vinales bounced back after an early crash to post the second best time at 0.387sec with Spain's world championship leader Marc Marquez of Repsol Honda third best at 0.483.

The session was red flagged twice, the first when Ducati's Michele Pirro suffered a spectacular high-speed crash.

Italian Pirro lost control as he braked while riding at about 350kmh, flying metres into the air before crashing onto the gravel and losing consciousness.

The 31-year-old was treated trackside and later transported by helicopter to the Careggi hospital in Florence for scans.

MotoGP's chief doctor Angel Charter confirmed later that Pirro had suffered concussion, neck, chest and back injuries and a dislocated shoulder. 

"He's moving all limbs normally and his neurological situation is normal," he added.

The session was again halted when Dovizioso's Ducati caught fire. 

The Italian - winner in Mugello last year - had been third overall after the morning session.

Iannone posted the fastest times in both sessions improving in the afternoon on his morning's performance.

"I've a good feeling. It's been a very positive day," said Iannone, looking to build on back-to-back third places in Austin and Jerez.

Italian star Valentino Rossi of Yamaha achieved the seventh fastest time.

The third practice session takes place on Saturday morning before qualifying for Sunday's race.

Combined times after first two free practice sessions:

1. Andrea Iannone (ITA/Suzuki) 1min 46.735sec, 2. Maverick Vinales (ESP/Yamaha) at 0.387sec, 3. Marc Marquez (ESP/Honda) 0.483, 4. Johann Zarco (FRA/Yamaha Tech3) 0.630, 5. Jack Miller (AUS/Ducati Pramac) 0.668, 6. Cal Crutchlow (GBR/LCR Honda) 0.698, 7. Valentino Rossi (ITA/Yamaha) 0.710, 8. Franco Morbidelli (ITA/Honda) 0.762, 9. Danilo Petrucci (ITA/Ducati Pramac) 0.834, 10. Jorge Lorenzo (ESP/Ducati) 0.956