Fernando Alonso was "on top of the world" after surviving a late Michael Schumacher attack to take his third consecutive victory in a thrilling San Marino Grand Prix.

The Renault man moved 18 points clear at the top of the drivers' championship with a faultless victory from second place on the grid.

But, unlike his previous two wins this season, Alonso was made to fight to the very end by a revitalised Schumacher, who started 13th but showed phenomenal pace to catch Alonso and harry the Spaniard until the chequered flag.

Alonso was ecstatic after winning by just 0.2 seconds following 11 laps of intense Schumacher pressure.

He said: "I am on top of the championship and on top of the world.

"It was probably one of the best fights I have ever had. It is my third win and the fourth for the team.

"We knew that here was a difficult weekend and I think we showed the performance of the car was competitive.

"Our race pace was not like Ferrari but we had an advantage on the grid. This is probably the best of the three I've won so far.

"It was difficult but, at the end, I managed to be first. Obviously, Michael was much quicker, more than a second faster than me."

Alonso, who took over at the front when McLaren's pole-position man Kimi Raikkonen retired on lap nine with a mechanical problem, revealed worries over the reliability of his engine had hampered his weekend.

New rules for this season mean engines must last two race weekends and after the exertion of winning in 42-degree heat in Bahrain, Alonso's power plant was a serious cause for concern.

"From Friday, we knew that maybe we had some problems with the engine, so we limited the laps on Friday and Saturday morning a lot," he said.

"That cost me a bit of time, in qualifying one especially, because it was only my third timed lap of the day.

"In the race, we were running very low revs and just trying to finish the race. I was expecting to be in the points and now I have won it."

Schumacher admitted he wasted Ferrari's "stunning pace" by making a mistake in qualifying. The world champion, who ran through the gravel and lost three seconds to put him down in 13th on the starting grid, conceded that error cost him victory.

He said: "I am happy in one way after the race and I am obviously quite excited but I am a bit disappointed because of what happened to me in qualifying.

"If you think through what could have happened if that didn't happen - it would have been a perfect day.

"I am just disappointed that it did happen. In one way, I should be not too worried because I don't do too many of those mistakes, but one is enough and it was a sad one. We have stunning pace and performance. It has been a tremendous effort from everyone, we were just flat out and it paid off."

Schumacher's charge through the field prevented Jenson Button equalling his best-ever result.

The BAR-Honda driver, who had not finished a race this season before yesterday, was running a comfortable second before he was added to Schumacher's list of victims. He continued to claim third and signal a return to form for BAR.

Alex Wurz, standing in for the injured Juan Pablo Montoya at McLaren, claimed a fine fourth place in his first race since 2000 while Takuma Sato confirmed BAR's revival by adding fifth place to Button's podium.

Former world champion Jacques Villeneuve scored his first points of the season with sixth for Sauber.

The Toyota pair of Jarno Trulli and Ralf Schumacher were seventh and eighth respectively but David Coulthard was down in 13th for Red Bull, twice clashing with Felipe Massa.