Lewis Hamilton of Mercedes won a wet Japanese Grand Prix which was abandoned with seven laps left on Sunday after Marussia driver Jules Bianchi crashed into a recovery vehicle.
The 25-year-old French driver is undergoing surgery for a severe head injury, FIA said in a statement.
Bianchi spun off the track and crashed into a recovery vehicle which was dealing with the damaged Sauber of Adrian Sutil.
Sutil had gone off at the same spot in the previous lap owing to aquaplaning. Bianchi underwent medical treatment on site before being taken to the circuit medical centre and then by ambulance to hospital.
"The CT scan shows that he has suffered a severe head injury and he is currently undergoing surgery. Following this he will be moved to intensive care where he will be monitored," FIA said.
"Mie General Hospital will issue an update as soon as further information becomes available."
Sutil, who escaped his incident unharmed and witnessed Bianchi's crash, said: "I hope he is OK. I don't want to say any more." The safety car came out and the race - which had also started behind the safety car owing to wet conditions - was stopped shortly afterwards and not restarted.
Hamilton passed team-mate and pole sitter Nico Rosberg in the 29th lap to win from him and world champion Sebastian Vettel of Red Bull.
Hamilton stretched his lead over Rosberg in the championship to 10 points - 266 to 256 - with his eighth season success and four races left. But the victory ceremony was very subdued in the wake of Bianchi's crash and no one in a festive mood. "It's not nice to hear one of our colleagues is seriously injured so that's the main worry," Hamilton said.
"Before that it was so enjoyable. You could see some commotion and the car was really badly damaged on the right. So we just hope he's OK."
Rosberg said: "I'm not thinking about the race, I'm thinking about my colleague. I've been given some information and it seems very, very serious. I'm hoping for the best."
Heavy rain in connection with approaching typhoon Phanfone lashed the Suzuka track and the unsafe conditions led to a start behind the safety car, a 15-minute stoppage after lap two, and then another seven laps with the safety car before the action really started.
Rosberg won the flying start into the 10th lap from Hamilton while ex-champion Jenson Button of McLaren was the first to come in for intermediate tyres.
Button's early stop lifted him to third, and world champion Sebastian Vettel fought his way up to fourth, followed by Red Bull team-mate Daniel Ricciardo.
Hamilton appeared faster than Rosberg, but unable to pass him, and had a scare entering lap 27 when he briefly lost control and rode out in turn one where he crashed in Saturday practice.
But two laps later the Briton was on top, storming past Rosberg at the end of the start-finish straight and keeping control into turn one this time around in the manoeuvre which decided the race.
The second round of pit stops followed between laps 30 and 37, just before new rain set in, with the flying Hamilton increasing his lead over Rosberg who had been complaining about oversteer.
Vettel rose to third despite riding out once, ahead of Button who had required a new steering wheel at the second stop and was in a fierce fight with Ricciardo.
Button was soon in for full wet tyres with 10 laps left while Sutil crashed his Sauber into the barriers - and Bianchi then crashed at the same spot as the track became slippery again.
FIA said that following Sutil's crash on lap 42 marshals displayed double waved yellow flags before the corner to warn drivers of the incident.
"A recovery vehicle was dispatched in order to lift the car and take it to a place of safety behind the guard rail. While this was being done the driver of car 17, Jules Bianchi, lost control of his car, travelled across the run-off area and hit the back of the tractor," its statement said.
The safety car came out again and the medical car sped to the crash site, while the race was red flagged shortly afterwards.
Fernando Alonso had to retire his Ferrari during the first safety car stage with a power failure. Alonso is expected to leave Ferrari after the season, with Vettel seemingly taking his place after saying Saturday that he leaving Red Bull.
The next race is the inaugural Russian Grand Prix in Sochi on October 12.
