MONZA (Italy) • Lewis Hamilton extended his lead, at least provisionally, in this year's drivers' world championship to 53 points yesterday when he drove to a flawless and consummate race in a typically dramatic Italian Grand Prix victory.

As nearest rival and Mercedes team-mate Nico Rosberg retired with a blown engine with two laps to go, Hamilton took full advantage as his perfect drive ended amid chaotic scenes and reports that he had raced with illegal tyre pressures on his car.

Hamilton led from pole position to the chequered flag, surviving a nervous period during the final laps when, warned by his team, he became aware of possible performance problems.

His points advantage, with seven races remaining, starting with the Sept 18-20 Singapore Grand Prix, makes him a clear favourite to defend his crown and claim his third world title.

The newly-blond defending two-time world champion came home in 1hr 18min 00.688sec - 25.042sec ahead of Sebatian Vettel of Ferrari.

Former local hero Felipe Massa finished third for Williams, crossing the line 0.3sec ahead of his Finnish team-mate Valtteri Bottas.

Kimi Raikkonen, who started on the front row with Hamilton, steered the second Ferrari to fifth place despite falling to last place in the opening lap.

Hamilton's win - assuming it is confirmed - was his second in succession at the Autodromo Nazionale, his third in all at the famous old circuit, his seventh of the season and 40th of his career.

"Those last few laps were not cool, man," Hamilton told his engineer over the team radio, after being asked to push harder and not ask questions.

It later emerged that Mercedes were under investigation for running illegal tyre pressures, with stewards reporting that the left rear tyre on Hamilton's car was 0.3 PSI below the minimum starting pressure specified by Pirelli.

A team representative was summoned to the stewards, with fears Hamilton could face a 25-second penalty, and possibly disqualification.

Asked about his allegedly irregular tyre pressures, the Briton said he knew nothing about it.

"I didn't know a thing," he said.

In his 50th race since joining Mercedes, Hamilton had made a perfect start as, behind him, Raikkonen stalled and, with cars weaving around him, Vettel powered into second place in pursuit of the championship leader.

Raikkonen's misfortune gave the two Williams cars a chance to take third and fourth with Massa leading Bottas behind Vettel, the top five stretched out by Hamilton's early speed as he opened a lead of 5.9 seconds by lap 10.

Rosberg, in a car fitted with an older Mercedes engine following a coolant leak on his updated new unit on Saturday morning, passed Perez for fifth, but found it more difficult to overhaul Bottas as the race order settled. His hopes then literally went up in flames when the German pulled over two laps from the end with smoke and flames billowing out from the rear of his car while in third place.

"It is a massive step in the wrong direction," said the German.

"I keep going. Giving up doesn't exist for me."

There was first-lap despair for the Lotus drivers with both Romain Grosjean and Pastor Maldonado both forced into retirement with mechancial problems.

AGENCE FRANCE-PRESSE, REUTERS