Sebastian Vettel's seemingly unstoppable march to a third straight Formula One title took another stride with victory in the Indian Grand Prix on Sunday, though the Red Bull driver's nearest rival, Fernando Alonso of Ferrari, kept up the pressure with a second-place finish.

Vettel won a fourth straight race in a season for the first time in his career - completing a clean sweep of the Asian swing - and now leads the drivers' championship by 13 points with three races to go. He is trying to join Juan Manuel Fangio and Michael Schumacher as the only men to win a hat trick of drivers' championships.

"It's pretty amazing (to win four straight races)," Vettel said. "It's very hard to target these kinds of things, they either happen or they don't happen."

The one-two finish of the top two drivers in the standings meant the fight for the title had now boiled down to a head-to-head fight in all but the mathematical sense. Asked if he had one hand on the championship trophy, Vettel suggested it was too close to call yet.

"The other one is probably Fernando's," Vettel said. "It's a big step for us but there is a long way to go and we know how quickly things can change."

Alonso acknowledged second was the best he could hope for on Sunday, but with upgrades to his car expected ahead of next week's Abu Dhabi Grand Prix, he still had faith that he could catch Vettel by the final round.

"It's not easy at the moment to fight with Red Bull but we never give up," Alonso said. "We want the joy in Brazil, not only here, and I am sure we will do it.

"There are still many points on the table, so I am still optimistic."

Red Bull's Mark Webber was running in second place until lap 48 of the 60 when the failure of his KERS power boost system allowed Alonso to sweep past on the main straight. The Australian then had to fight hard to hold off McLaren's Lewis Hamilton in the closing laps, sneaking into the final podium position by just six tenths of a second.

"It's so demoralizing on that straight with no KERS," Webber said. "I was a moving target really."

McLaren's Jenson Button was fifth, while Ferrari's Felipe Massa held off Kimi Raikkonen of Lotus in a race-long dogfight in which the pair was rarely more than a second apart. Force India's Nico Hulkenberg, Lotus' Romain Grosjean and Williams' Bruno Senna took the final points positions.

When told that he was the first man since the late Ayrton Senna in 1989 to lead every lap of three straight races, Vettel appeared emotional, saying: "It's really, really special. We all remember Ayrton forever."

Vettel's only moment of concern came at the beginning of the race when Webber got off to a slightly better start, and the German shifted sharply to his right to block his teammate's run, though the Australian said the move was "fair enough."

The main casualty on the first lap was Schumacher, who suffered a right rear puncture when his Mercedes was hit from behind by Toro Rosso's Jean-Eric Vergne. Forced to complete most of a lap on a wheel rim before he was able to pit, Schumacher's race was effectively over.

Alonso got a great run out of the third-turn hairpin and was able to move past both McLarens on the main straight even without the benefit of the DRS open wing, and that proved decisive in his second-place finish.

The race quickly settled into a pattern, with all drivers able to go for a single pit-stop strategy on the very smooth Buddh surface.

Sauber's Sergio Perez retired on lap 19 after his right rear clipped the front wing of Daniel Ricciardo's Toro Rosso.

Webber was running in second, within 5.4 seconds of Vettel after lap 21 when his KERS started to malfunction, allowing the German to almost double that advantage over the next four laps, and from there the result was never in doubt.