Lewis Hamilton and Fernando Alonso have paid emotional tributes to Ayrton Senna as the 20th anniversary of the death of the maverick Brazilian superstar and three-time world champion nears.

Senna, widely regarded as the greatest racing driver of all time, died when his car careered off the Imola track in the early stages of the San Marino Grand Prix on May 1, 1994.

He was 34 years old.

It was Formula One’s blackest weekend, which also saw Austrian rookie Roland Ratzenberger killed and Senna’s compatriot Rubens Barrichello injured.

“When I was a kid I had all the books, all the videos, he was the driver I looked up to,” said Hamilton, who was just nine at the time of Senna’s death.

“He inspired me to be a driver and on the day of his passing, … it was very difficult for me to show my emotions so I went off to a quiet place and it was very difficult for several days … your hero’s gone.”

Senna, the outspoken world champion of 1988, 1990 and 1991, was leading in San Marino on lap seven when his Williams car veered spectacularly off the racing line at more than 300km/h at the Tamburello corner and straight into a concrete wall.

He received emergency treatment at the scene before being airlifted to Bologna hospital where he was later declared dead.

“He was an incredible legend. You like to think that one day you may be recognised as someone that was able to drive similarly to him,” added Hamilton, the 2008 world champion.

Alonso, the 2005 and 2006 world champion, was 12 when Senna was killed and the Spaniard vividly recalls the day of the tragedy.

“On my schoolbooks I didn’t have pictures of girls, obviously I was too young but I had Ayrton there and the same in my room,” said the Ferrari star.

“I had a big poster of Ayrton and even my first go-karts were in the colours of Ayrton’s McLaren because my father also liked him. It was a very sad moment.”

Senna himself admitted that he feared for his safety in the 1994 season after a series of technical changes were made to the sport.

“It’s going to be a season with lots of accidents, and I’ll risk saying that we’ll be lucky if something really serious doesn’t happen,” warned Senna in a chilling premonition.

AAP