MONZA, Italy — Sebastian Vettel drove to an easy victory in his Red Bull at the Italian Grand Prix on Sunday, winning his eighth race of the season and extending his grip on the championship lead. With six races left in the series, he is in an unassailable position.

Vettel, a German, started in the pole position and was challenged only briefly when Fernando Alonso drove his Ferrari past the Red Bull by the first corner on the first lap, bringing the Italian fans to their feet. But it was not to last: the Ferrari was no match for the Red Bull.

It was Vettel’s 18th career victory. His first win, in 2008, was also at Monza, but in a Toro Rosso car.

“The circuit means a lot to me and has been very special,” he said. Referring to his first victory here, he added, “When I crossed the line I remembered every bit of it.”

Alonso finished in third. Jenson Button, in a McLaren Mercedes, was second.

But most of the excitement — aside from an accident at the first corner that took out five cars — was a battle between Lewis Hamilton and Michael Schumacher for fourth.

For Schumacher, who has won the world title seven times and returned in 2010 from three years in retirement, it was one of the  most impressive races of his comeback. He and Hamilton raced wheel to wheel for half of the 53-lap race before Hamilton finally passed Schumacher and held on to fourth after 27 laps.

Schumacher finished fifth.

On the last lap, Hamilton went after Alonso, but he failed to pass him, and they crossed the line half a second apart, allowing the Italian fans to celebrate a Ferrari on the podium.

Nine cars failed to finish the race.

Bruno Senna, the nephew of the triple world champion Ayrton Senna, who died in a racing accident in 1994, finished in ninth position, scoring his first points in the series in his second race this year for the Lotus Renault team. Senna had entered the series with the HRT team last year.

In order to win the title, Vettel needs only to finish in the top three at the next race in Singapore in two weeks.

“It has been an incredible year so far, and last year to this year we made an incredible step,” Vettel said. “I love racing; we enjoy racing as a team together every weekend. Unpacking the car, you can see the passion.”