English driver Justin Wilson was declared dead on Monday after suffering a severe head injury during an IndyCar race in Pennsylvania, plunging the sport into mourning and triggering calls for a review of safety measures.

Wilson, 37, had been in a coma since Sunday, when a large piece of debris from another racer's car struck his helmet on the final laps of the "Tricky Triangle" of Pocono Raceway in the penultimate race of the season.

Friends and loved ones of the Sheffield-born racer had flown to be at his bedside at Lehigh Valley Health Network Cedar Crest Hospital in Allentown earlier Monday before his death was announced.

"This is a monumentally sad day for IndyCar and the motorsports community as a whole," said Mark Miles, chief executive of the parent company which runs IndyCar and the Indianapolis Motor Speedway.

"Justin's elite ability to drive a race car was matched by his unwavering kindness, character and humility -- which is what made him one of the most respected members of the paddock.

"As we know, the racing industry is one big family, and our efforts moving forward will be focused on rallying around Justin's family to ensure they get the support they need during this unbelievably difficult time."

Wilson's Andretti Autosport team paid tribute to him, describing him as a "tremendous racer, a valuable member of the team."

"We are deeply saddened by the passing of Justin Wilson," Andretti Autosport said in a statement.

"While Justin was only part of the Andretti lineup for a short time, it only took a second for him to forever become part of the Andretti family.

"His life and racing career is a story of class and passion surpassed by none.

"Our thoughts and prayers remain with the Wilson family and fans worldwide."

Wilson was hit by what appeared to be a section of fellow driver Sage Karam's car after it spun out on lap 179 of the 200-lap race.

The father-of-two was airlifted to the hospital immediately after the crash, and never regained consciousness.

Wilson had driven in major US open-wheel racing since the 2004 season.

He was driving a partial schedule in 2015 for Andretti, making his 174th IndyCar start. He recorded seven wins in CART and IndyCar races, his most recent coming at Texas in 2012.
Source: AFP