F1: Fernando Alonso brings Ferrari victory in Italian Grand Prix

Fernando Alonso celebrates

Alonso has now closed the gap to 21 points on new championship leader Mark Webber who finished sixth, the Australian deposing McLaren's Lewis Hamilton after he crashed out on the opening lap.

Jenson Button, who led for the first 36 laps until ousted from top spot by Alonso in the pit stops, finished second, with Felipe Massa third in his Ferrari.

Red Bull conjured a magnificent strategy for Sebastian Vettel as he pitted at the end of the penultimate lap after having opened up a 22-second gap on fifth-placed Nico Rosberg in his Mercedes.

It was enough of an advantage for him to retain fourth spot, making amends in part of his indiscretions in the last two grands prix in Hungary and Belgium.

It means with five races of an enthralling season remaining, just 24 points - a race victory these days - separate the top five.

The McLaren duo, though, could not have imagined such contrasting fortunes at the start, with Hamilton paying the ultimate price for the strategy he adopted for qualifying.

Button opted to run with the f-duct - the aerodynamic device that increases straightline speed, and a higher rear-wing setting.

Hamilton chose to go without it and a much lower degree of rear wing, resulting in their grid placings of second and fifth.

It meant for the start Hamilton was in a fiercely competitive pack, sandwiched by the Red Bulls of Webber and Vettel, and with Massa directly ahead of him.

As it transpired, once the five red lights disappeared, Hamilton was untroubled by either Red Bull, comfortably passing Webber off the line and running in fourth as the field approached the first of the three chicanes, Rettifilio.

Ahead of him, Button had superbly edged past Alonso, despite the Spaniard's fierce attempt to cut across the Briton on the long run down to Rettifilio.

It was at the second chicane where Hamilton, though, came to grief as he attempted to cut up the inside of Massa who ultimately had the line.

As the Brazilian held his ground his rear-left wheel collided with Hamilton's front right, instantly breaking the suspension, sending him into the gravel and retirement - his second in the last two races.

It was also Hamilton's second successive retirement in this race after crashing out on the last lap a year ago when running third and as he attempted to pass Button, then with Brawn GP.

As expected, as the news of Hamilton's exit filtered around Monza, the tifosi (Ferrari fans) erupted with delight.

Explaining his accident, Hamilton said: "I had a good start and gained a position, and in a realistic world I perhaps should've stayed there a while.

"I put my car up the inside and tried to get third - it was obviously a little bit too much. It's my fault. I take the blame.

"I'm very disappointed in myself and sorry for the team. I've got to try to collect my thoughts and move onto the next race.

"The championship is not over, but it's mistakes like I made today that lose world championships."

What then followed was an intriguing game of cat and mouse between Button and Alonso, with the former hounded by the latter over the first 10 laps as there was barely a car length between them.

When Button finally set his first fastest lap on 11 he gave himself marginal breathing space, opening up a gap of exactly a second that increased to 1.6secs two laps later.

Remarkably, that was as good as it got for Button all afternoon as Alonso would reel him, then the Briton would edge away, only for the double world champion to close again.

It became apparent it was all going to come down to the one round of pit stops as to whom would claim victory.

On lap 36 Button took the initiative and came in ahead of Alonso, followed by the Spaniard a lap later, exiting his pit box just as Button was heading down the long home straight.

But as the 29-year-old returned to the track, he had his nose ahead of Button, and that was that, race over - third win of the season and 24th of his career in his pocket.

Massa finished within 4.2secs of Alonso, the top trio 24 ahead of Vettel, followed by Rosberg, then Webber who had brilliantly passed Williams' Nico Hulkenberg a few laps from the finish.

Renault's Robert Kubica, seven-times champion Michael Schumacher in his Mercedes and Rubens Barrichello for Williams completed the top 10.

After taking the acclaim of the thousands of tifosi (Ferrari fans) who had gathered beneath the podium for the anthems and champagne spraying, Alonso was naturally all smiles.

"It's something only that can be compared with my Spanish Grand Prix win of 2006. This is a very special feeling," said Alonso.

Assessing the championship picture, Alonso said: "Any good result gives you extra confidence and good motivation to keep working hard.

"But we know one race can change the positions in the championship a lot given the new points system this year.

"We need to remain calm and find some consistency in the last five races, which are now very important.

"This result gives us good motivation, but we need to enjoy tonight and the next couple days, and then we think of the championship later on."

Button still felt his wing strategy was "the right choice," adding: "The initial getaway went better than according to plan.

"The race was then pretty tough as I had Fernando in my mirrors the whole time, but I was able to defend.

"For me everything was going smoothly, but then we pitted one lap later, which might have been a mistake because I couldn't find any grip on the new tyres, and that's where I lost my time.

"It's a happy day, good points for the championship, but sad not to be on that top step."

Massa, explaining the incident with Hamilton, said: "I just felt something on my back - it was Lewis, he touched me, but I didn't see what happened. I just felt something.

"Overall it was a great race, especially when you come here and see all the fans on the home straight celebrating the way they did."