Lewis Hamilton has fired an ominous warning to his rivals by rating his best ever start to a Formula One season as "average".

Hamilton's win in Monaco on Sunday moved him to four victories from the first six rounds of his championship defence.

Following two second places, it marks Hamilton's greatest opening to a campaign in his 13-season career.

Hamilton scrambled to the chequered flag in Monte Carlo after Mercedes made a mistake by putting him on the less-durable medium tyres with 68 laps of the race still to run.

The call was taken by James Vowles, Mercedes' chief strategist, and Hamilton got his own back by drenching him, and Mercedes' chief race engineer Andrew Shovlin, in champagne midway through the team's post-race debrief.

"That's for putting me on those f****** tyres for 68 laps," a laughing Hamilton said in a video posted to Instagram by Mercedes.

"You said the tyres wouldn't make it to the end," said Shovlin in response.

The world champion replied: "They f****** didn't make it to the end. I made it to the end."

Vettel may have ended Mercedes' run of one-two finishes after taking second place in Monte Carlo.

Both Hamilton and Vettel are expected at Niki Lauda's funeral, which is due to take place in Vienna on Wednesday.

The Mercedes' non-executive chairman died last Monday nine months after a double lung transplant.