Mercedes driver Lewis Hamilton took his 90th Formula 1 win on Sunday in a chaotic Tuscan Grand Prix that was red-flagged twice and involved two multi-car collisions.

While consensus among the F1 fraternity was that the Italian Mugello circuit's fast sweeping turns and frequent undulation would be the season's biggest physical challenge for the drivers, there were fears that a lack of heavy braking zones would make overtaking difficult.

However, any concerns over a processional race were dispelled in a surreal opening few laps.

A concertina effect after the first start saw the slow-starting Red Bull of Max Verstappen - who had had engine trouble before the race had even started - and Pierre Gasly's AlphaTauri pushed off into the gravel at turn 2, resulting in the deployment of the safety car to clear the stricken vehicles.

When the safety car pulled in on lap 7, Valtteri Bottas, who had overtaken teammate Hamilton to lead after the first start, unusually elected to bunch the pack up until after he had crossed the start-finish line.

As a result, several drivers towards the rear of the field misjudged the return to racing speed and ploughed into slower cars in the midfield, instantly wiping five drivers out of the race and causing stewards to issue a halt to proceedings to allow marshals to clear the debris.

Though several drivers were critical of the manner in which Bottas had led the restart, race stewards took no action against the Finn, who lined up for the race's second standing start on lap 9 from pole position.

However, in a reversal of fortunes from the previous getaway, this time Hamilton got the better start and jumped Bottas to take the lead.

With the two Mercedes once again the class of the field and pulling away from the rest, much of the interest in the race took place further down the order, as Ferrari's Charles Leclerc was unable to hold onto his third place and was soon passed by several rivals - an embarrassing state of affairs for the storied Italian squad on their 1000th Grand Prix start.

Perhaps mindful of its drivers' tyre troubles at Silverstone earlier in the season, Mercedes engineers ordered Hamilton and Bottas to stay off the Mugello circuit's kerbs - though even after doing so, both drivers appeared to have enough pace to keep the chasing pack at bay.

But just when it appeared as if the race had settled into a predictable rhythm, the Racing Point of Lance Stroll suffered a puncture on lap 43 that sent the Canadian careening off the circuit at high speed.

This initially saw another deployment of the safety car, before race stewards decided that clearing the wreckage and repairing damage to the barrier would be better done with the race temporarily halted again.

The Tuscan Grand Prix's third start on lap 47 saw Hamilton keep his lead, with the Renault of Daniel Ricciardo briefly passing Bottas for second before relinquishing the place after one lap of racing.

Red Bull's Alex Albon also passed Ricciardo and looked briefly as if he might be able to challenge the two Mercedes, but his initial pace proved a false dawn as Hamilton duly took his sixth win of the season ahead of Bottas.

"It was all a bit of daze," said Hamilton, who also took home the bonus point for fastest lap. "It was like three races in one day. Just incredibly tough. This track is phenomenal and keeping Valtteri behind was not easy. [With] all those restarts, total focus was needed. My heart is racing. It is crazy to be here and to have 90 Grand Prix wins."

Behind Bottas, Albon scored his first ever podium finish to ease some of the pressure on him after a trying year. Ricciardo took fourth ahead of Stroll's teammate Perez, while Lando Norris finished sixth in his McLaren.

Daniil Kvyat took a fine seventh in his AlphaTauri, with Leclerc and teammate Sebastian Vettel salvaging eighth and ninth on another difficult day for Ferrari.

Alfa Romeo's Kimi Raikkonen rounded out the top ten after an eventful race in which he also received a five-second penalty for a pit-lane infringement.

Hamilton's win sees him extend his lead in the driver's championship to 190 points, ahead of Bottas on 135 and Verstappen on 110.

In the constructors' standings, Mercedes remain well out in front on 325 point, with Red Bull second on 173 and McLaren third on 106.

The next round of the 2020 Formula 1 championship is the Russian Grand Prix at the Sochi Autodrom on September 27.