Sebastian Vettel 'speechless' after sealing fourth world title in row

Red Bull's Sebastian Vettel said he was "overwhelmed" to win his fourth consecutive world title, after victory in Sunday's Indian Grand Prix.

The German is the only the fourth man to become a four-time champion, after Juan Manuel Fangio, Alain Prost and Michael Schumacher.

"I'm speechless - I don't know what to say. It's one of the best days of my life so far," he said.

"It has been incredible to race some of the best drivers F1 has ever had."

He added: "It is a very strong field and to get the numbers and statistics we have is unbelievable."

Vettel sealed the 2013 championship with victory in India, his 10th win in 16 races so far this season.

The 26-year-old has won six races in a row and if he wins the remaining three races in Abu Dhabi, the United States and Brazil he will equal the record for consecutive wins in the F1 world championship, set by Italian Alberto Ascari in 1952-53.

Vettel celebrated by doing 'doughnut' spins on the pit straight after his slowing-down lap and then bowed to his car, a gesture he said was to show his appreciation for his team.

And he said he was having difficulty coming to terms with the scale of his achievement.

"Fangio did five and everybody appreciated him as the best driver in the world. Michael came along many years later, different time, different era - I am just talking as a fan - he had a very dominant car but he created that in Ferrari.

"He was working very hard - he worked harder than anyone else. He had some tough challenges - [Juan Pablo] Montoya, Kimi [Raikkonen], David [Coulthard], Fernando [Alonso] - and it is incredible one guy managed to score more titles than this guy [Fangio] did.

"To join people like that is very difficult for me to put into perspective. I am far too young to understand what it means."

Vettel also paid tribute to his leading rivals of the current era, particularly Alonso, who has this year been his closest rival for the third time in four years. The Spaniard's hopes this season finally died with an 11th-place finish in India after he damaged his front wing on the first lap.

"I was watching TV when Fernando started to win races [in 2003] and now I'm racing Fernando," Vettel said.

"He has been my toughest opponent behind the wheel. He is very gifted.

"He is Spanish, very passionate. To race people like him and Lewis [Hamilton], who has an amazing level of natural talent, and Mark [Webber, Vettel's team-mate], who I rate the same way, Nico [Rosberg], who I think is underestimated, a lot of guys, you know, Kimi, Jenson [Button]…

"To win four titles [against them], I don't know, it is a big number."