Max Verstappen said it was a "crazy feeling" to retain his Formula One world championship Sunday in dramatic fashion after winning a rain-shortened Japanese Grand Prix and then seeing his nearest rival Charles Leclerc relegated to third by a five-second penalty.

The result gave Red Bull driver Verstappen an unassailable 113-point lead in the championship, making him only the third driver after Michael Schumacher and Sebastian Vettel to clinch the title with four races to spare.

Ferrari's Leclerc crossed the line second in front of Red Bull's Sergio Perez, but he was hit with a penalty after squeezing Perez in the final chicane and being deemed to have gained an advantage by leaving the track.

Verstappen was only informed he had retained his title midway through the post-race TV interview, and even the driver himself was not sure if he had sealed the deal.

"It's a crazy feeling of course as I didn't expect it when I crossed the line," said a surprised Verstappen.

"Was it going to be half points? I didn't know how many points I was going to get. I was happy with the race we had."

The race got off to a chaotic start in heavy rain.

Leclerc was quicker off the line than pole sitter Verstappen, who admitted he made "a terrible start", before the Dutchman regained the lead with a brave overtake around the outside of turn one.

"It was very close but that's what people like to see," Verstappen said.

Ferrari's Carlos Sainz spun out on the first lap and the Williams of Alex Albon broke down prompting a safety car.

A red flag soon followed and forced the drivers back to the pit lane for more than an hour before the action restarted at the second time of asking under a safety car rolling restart.

Verstappen resumed with a lead over Leclerc and Perez and extended it with ease once the safety car period ended and track conditions gradually improved.

- 'Congratulations to Max' -

"It was very difficult and they made the right call," Verstappen said of the red flag.

"The first time they tried to restart it was not right. Once we got going it was fine."

Verstappen took the chequered flag but there was a furious battle for second behind him, with Leclerc cutting across a corner while jostling for position with Perez.

Leclerc beat Perez to the line but later conceded that his penalty was "the right thing to do".

"I don't have much to say -- I made a mistake and tried to minimise it," said Leclerc, who led the championship early in the season.

"Huge congratulations to Max and Red Bull. Max has been incredible and it's a title fully deserved."

Verstappen has won 12 of 18 races in 2022 and thanked his team for an "incredible" year.

"The first (championship) is a little more emotional, the second one is beautiful," he said.

"It's been a special year, and you need to remind yourself as these kind of years you don't have very often."

Red Bull team principal Christian Horner said Verstappen had "grown" as a driver.

"Carrying that number one this year, he's done it with a lot of pride," he said.

French driver Pierre Gasly reacted furiously after passing a tractor on the track early in the race.

AlphaTauri's Gasly said he could have been killed after encountering the vehicle, which was deployed to recover Sainz's car.

It brought back painful memories of the tragic 2014 race at Suzuka, when another French driver Jules Bianchi died after colliding with a recovery vehicle in poor conditions.

That prompted a review of safety and the introduction of the "halo" cockpit head protection system for drivers.