Renault's Formula One driver Fernando Alonso (C) of Spain celebrates with his team's mechanics after finishing third in the Brazil Grand Prix in Sao Paulo September 25, 2005. (Reuters)

Spain's Fernando Alonso became Formula One's youngest world champion with a solid third place in the Brazilian Grand Prix at Interlagos on Sunday.

It gave the 24-year-old Renault driver an unassailable lead over Finn Kimi Raikkonen who finished second behind McLaren team-mate Juan Pablo Montoya.

The McLaren one-two sees them take the lead in the constructors' championship by two points over Renault with two rounds remaining.

But this will be scant consolation after another mature performance from Alonso, who started from pole positiion but conceded the lead to Colombian ace Montoya early in the race.

Raikkonen, who moved through from fifth on the grid, took over from Alonso in second place after the first round of two pit stops, but had to rely on the Spaniard having a mechanical failure in the ever-reliable Renault.

Seven times champion Schumacher finished fourth, ahead of Italian Giancarlo Fisichella in a Renault and Brazilian Rubens Barrichello in the second Ferrari.

Briton Jenson Button was seventh for BAR with Ralf Schumacher taking the final point for Toyota.

Williams, whose last win was at Interlagos with Montoya at the end of last season, had a miserable afternoon with both cars colliding at the start.

In a crash that brought out the safety car for one lap, Brazilian Antonio Pizzonia hit the Red Bull of Briton David Coulthard and then his own team-mate Mark Webber seconds after the start lights went out.

Renault boss Flavio Briatore was quick to praise Alonso after bringing the world title to his team for the first time.

"It has been a fantastic championship and Fernando is a fantastic champion. We have been fighting to the end and he has done the best for the performance we have at this moment.

"He has been so consistent this year. His one mistake was in Canada and other than that he has been fantastic. He is terrific."

(Agencies)