Fernando Alonso seized a longed-for victory in his first Italian Grand Prix for Ferrari on Sunday while Lewis Hamilton lasted less than a lap and handed the championship lead back to Australian Mark Webber.

It was Ferrari's first Formula One win at their home circuit since Michael Schumacher's victory in 2006 and Alonso answered the fans' prayers despite being overtaken at the start by McLaren's world champion Jenson Button.

Button, who led for more than half the race by little more than a second, finished runner-up after losing out at his pitstop after 36 of the 53 laps.

With Button's team mate Hamilton going out on the first lap, Red Bull's Webber surged five points clear despite finishing only sixth.

The top five are now separated by just 24 points, less than the 25 available for a victory, with everything to play for and five races remaining.

Webber has 187, Hamilton 182, Alonso 166, Button 165 and Red Bull's Sebastian Vettel 163.

Button denied Ferrari a one-two finish, with Brazilian Felipe Massa joining team mate Alonso on the podium in third as a sea of red-shirted fans invaded the track in jubilation.

"This is a good motivation for all of us but the remaining five races are the really important ones," said Alonso, who started on pole position and had earlier described Monza as crucial to his hopes of a third title after he crashed in Belgium last month.

"We need to remain calm. This was a good weekend for us. Spa was a bad weekend. We need to find some consistency in the final races."

New Formula One championship leader Mark Webber was already looking forward to the more Red Bull-friendly Singapore track in the next grand prix after trailing home sixth in Italy on Sunday.

The Australian's car was never likely to threaten at super-fast Monza, but the early exit of Lewis Hamilton allowed Webber to leapfrog the Briton and take a five-point lead with five races left.

"I'm sure I'll be pretty happy when I think about it," the tall Webber said as he balanced the emotions of being the leader against the disappointment of being off race pace.

The Singapore race, next up on September 26, is on a street track which will better suit the Red Bulls' characteristics.

"I think it can be a good race for us for sure," he added.

Massa had challenged Alonso at the start, a seemingly futile gesture for a driver ordered to let the Spaniard win in Germany, but his main contribution was to knock Hamilton out of the running at the Della Roggia chicane on the opening lap.

The two banged wheels in a risky bid by the 2008 champion for third place and Hamilton's front right suspension was broken by the impact.

Hamilton's retirement was his second in three races, although he won the previous race in Belgium, and his second in succession in Italy.

"The championship is not over but it's mistakes like I made today that lose world championships," the Briton told reporters. "It's my fault, I'll take the blame."

Vettel was fourth, leaving his pitstop to the last lap after earlier suffering an engine problem and slipping behind Webber.

He cut his deficit to Webber from 28 to 24 points, with his result demonstrating that Red Bull were in no mind for the 'team orders' that led to Ferrari being hauled before the governing body last week.

Germany's Nico Rosberg was fifth for Mercedes with compatriot Nico Hulkenberg seventh for Williams.

Poland's Robert Kubica was eighth for Renault with Schumacher ninth in a Mercedes and Brazilian Rubens Barrichello, last year's winner for Brawn GP, taking the final point for Williams.

While Webber was in thoughtful mood, team mate Sebastian Vettel was grinning from ear to ear after the huge gamble of pitting on the last lap paid off.

"It was quite exciting, especially the last lap," he smiled.

"Obviously if it works you are the king, if it doesn't you are an idiot. Fortunately it worked out today."

This season's new points system offers 25 points for a race win, meaning Vettel is still very much in the fight.

"This year the points system makes people more nervous and more excited. All we can do is achieve the maximum, which today was fourth," he said.

"We are doing everything we can to win the championship."