A simmering battle in Formula One erupted in spectacular fashion as championship leader Max Verstappen and defending champion Lewis Hamilton crashed out of the Italian Grand Prix, with Hamilton crediting the halo for saving his life.

As both Hamilton and Verstappen fought for position midway through the race, their cars came together in a move that could have seriously injured Hamilton.

Mercedes team principal Toto Wolff went as far as describing it as "a tactical foul" by Verstappen.

"The stewards will decide who is to blame," Wolff said. "In football you would call it a tactical foul. He knew that if Lewis stays ahead, then that is the race win."

In the end, the stewards did decide, judging that Verstappen "was predominantly to blame for the collision".

They gave the Red Bull driver a three-place grid drop for the start of the next race, the Russian GP on September 26.

"I'm proud of the stewards," Hamilton said after learning of their decision.

"I need some time to really reflect on it but I think it definitely sets a precedent and I think it's important for us, moving forwards, for the safety of the drivers, that there are strict rules set in place."

The crash led to the right rear tyre of the Red Bull landing on the protective halo of the Mercedes, above Hamilton's head.

The halo is a curved titanium bar that sits above the cockpit and is designed to protect drivers' heads from large impacts.

While being one of the lightest parts on the car, Formula One said prior to its introduction that it can withstand the weight of 12,000 kilograms.

Hamilton, who had been outspoken against the protective halo before it became mandatory in 2018, thinks it may have just saved his life in this instance.

"I don't think I've ever been hit on the head by a car before. It's quite a shock for me," added Hamilton, who still sounded distressed several hours after the incident.

"And I've been racing a long, long time.

"Honestly, I feel very, very fortunate today. Thank God for the halo. That ultimately saved me and saved my neck. I think in the actual moment it was a big hit, but all I could think was to get going again.

Verstappen maintained his championship lead, which he had slightly extended to five points by coming second in the sprint the day before.

"We were racing for position today but you need two people to work together to make the corner and Lewis just kept squeezing until there wasn't room anymore for two cars and that's when we crashed," Verstappen said.

"I was there to try and race hard but fair.

"It's very unfortunate what happened today but we are both professionals and so we will move on."

It was the second major incident between the two in as many months.

They clashed on the first lap of the British GP in what Red Bull called a "desperate" move by Mercedes driver Hamilton that saw him given a 10-second penalty and Verstappen hospitalised.

On this occasion, the biggest talking point of the race came on Lap 26.

Hamilton had pitted from the lead and returned to the track just in front of Verstappen.

Verstappen then tried to come up the inside on a turn as the seven-time champion defended his position.

As the two made contact, Verstappen's car catapulted on to the top of the Mercedes as both slid into the gravel.

Both drivers were able to walk away from their cars, although Hamilton took a long time getting out of his, only clambering out after Verstappen had long gone.

"I did see Max get out and just walk by," Hamilton said.

"I felt that a little bit surprising because, ultimately, when we do have incidents, the first thing we want to make sure is that the other guy that we crashed into is okay.

Ricciardo celebrated in his traditional style on the iconic Monza podium, drinking champagne from his shoe — and then getting teammate Lando Norris to do so too.

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It was McLaren's first win in nearly nine years, since Jenson Button took the chequered flag in Brazil in 2012, and Ricciardo's first win since Monaco in 2018.

The Australian finished 1.747 seconds ahead of Norris and 4.921 ahead of Mercedes driver Valtteri Bottas, who turned in a strong performance after starting from the back of the grid after a penalty for taking a new engine.

"Even if we got the start it wasn't guaranteed that we'd lead the whole race. We didn't have mega speed but it was enough to keep Max behind.

"To lead, literally from start to finish, I don't think any of us expected that. But there was something in me Friday, I knew something good was to come."