Lewis Hamilton wins the 2015 Italian Grand Prix

The reigning world champion made a clean getaway to lead away from pole, while Rosberg slipped back to sixth, and front-row starter Kimi Raikkonen fell to the back of the field.

Hamilton dominated the race from there, but with a few laps remaining, he was told by his team that he needed to push without being given a reason for doing so.

Hamilton did as he was told and took the chequered flag with a 25-second lead over Ferrari's Sebastian Vettel.

After the race Mercedes was referred to the stewards because its tyres were measured below Pirelli's 19.5psi guideline on the grid just before the race.

Meanwhile, there was more drama for Mercedes as Rosberg's engine expired with a few laps to go when the German was running third and catching Vettel.

It was the first mechanical retirement for Mercedes this season and comes after Rosberg had to revert to an old engine, which had done six races, after an issue with his upgraded unit.

It means Hamilton, who secured his seventh win of the season, now leads Rosberg by 53 points in the championship with seven races remaining.

Williams' Felipe Massa inherited third, with team-mate Valtteri Bottas fourth and Raikkonen fifth after a strong recovery drive.

Force India's B-spec car continued to impress with Sergio Perez following up his fifth place finish at Spa with sixth at Monza, one place clear of team-mate Nico Hulkenberg.

It moved the Silverstone-based team back ahead of Lotus into fifth place in the constructors' championship, after Lotus's race lasted just a couple of laps.

Romain Grosjean and Pastor Maldonado both suffered contact at Turn 1, with Grosjean pulling off track and Maldonado recovering to the pits and parking the car in the garage.

Red Bull's Daniel Ricciardo recovered from starting 19th after a 25-place grid penalty for changing engine elements to finish eighth with team-mate Daniil Kvyat 10th.

Sauber's Marcus Ericsson scored points for the third successive race with ninth.

Carlos Sainz Jr just missed out of points in 11th, one place head of Toro Rosso team-mate Max Verstappen, who started last and had to serve a drive-through penalty as punishment for his team releasing his car without its bodywork secure in qualifying, 12th.

Felipe Nasr was 13th for Sauber ahead of McLaren's Jenson Button, who made a blistering start to rise from 15th to ninth before dropping back.

The Manors of Will Stevens and Roberto Merhi brought up the rear with McLaren's Fernando Alonso retired with three laps to go.

ITALIAN GP RESULT - 53 LAPS:

DRIVERS' STANDINGS

CONSTRUCTORS' STANDINGS