Toro Rosso's Sebastian Vettel is on pole for the Italian GP on a grid mixed up by heavy rain during qualifying.

Lewis Hamilton qualified 15th following a strategic error. Title rival Felipe Massa was sixth, with Ferrari team-mate Kimi Raikkonen only 14th fastest.

Hamilton was eliminated in the second session because he was on the wrong tyres when the track was at its driest.

McLaren team-mate Heikki Kovalainen was second ahead of Red Bull's Mark Webber and Toro Rosso's Sebastien Bourdais.

The result sparked wild celebrations in the Toro Rosso pit, and will lead to expectations for a thrilling race as the front-runners try to work their way through the field.

Vettel, 21, replaces double world champion Fernando Alonso as the youngest man to take pole position in Formula One history.

"Unbelievable," he said. "Incredible. I was talking with my engineers and we said if it's wet we have to go for pole position, it was difficult. The most difficult part was Ascari where there was so much water.

"I never dreamt of being on pole. I wasn't very happy with the car in the wet yesterday but we made some changes overnight and it was much better today. And when you are confident in your car it is much easier in the wet.

"There was no real secret. We did more or less the best we could in running out there.

"It always depended on the conditions. In the second session it was quite difficult. I set my time quite early, and it got wetter and wetter, so the ones who delayed going out had a bit of bad luck."

The forecast is for more wet weather on Sunday, and it is expected to be the first wet race at Monza since 2004.

There have only been four wet races here in the entire history of the Italian Grand Prix.

Webber said: "I don't think anyone wants to race in those conditions. There are some safety concerns at this place because of the high speed."

Hamilton and McLaren will be ruing their decision to go out on intermediate tyres – at the start of the second elimination session.

The rain had briefly abated after the first session, but the track was too wet for intermediates, which are designed to work in drier conditions than the full wet weather tyres chosen by most of his rivals.

Kovalainen said: "I don't know exactly what happened with Lewis. We decided to stay on the same set of tyres at the start of second qualifying. Lewis probably thought it would have been dry enough for intermediate tyres."

Even so, it was not a great performance from Hamilton.

He set his best lap at the same time as Massa – and the Brazilian's was two seconds faster and quick enough to get him into the top 10 shoot-out.