He walked away from the crash but was later taken to hospital where it was discovered he has a broken vertebra.
“Not sure the recovery time but hope to be back in the car as soon as possible,” he wrote on Instagram.
Another blow for Vettel
Vettel has now been out-qualified by Leclerc for seven races in a row and the session did not go his way.
He set his first lap without a tow after the Ferraris followed the Mercedes out only to see the silver cars pull over at the end of the pit lane. Vettel hesitated, thought about stopping behind them, but then accelerated away.
In the circumstances, he did well to lap within 0.15secs of Leclerc.
The Monegasque said the original plan was for Vettel to tow him on the first runs and then Leclerc to return the favour on the seconds.
But in the chaos of the dying seconds, Vettel first overtook Leclerc early on the warm-up lap as the cars jockeyed for position.
Leclerc then passed Vettel before Parabolica on instruction to the team, but Vettel did not cross the line in time to do a lap.
Behind the top four, Ricciardo was in excellent form in the Renault, which lacks downforce but has a strong engine and goes well on this type of track.
The Australian was 0.21secs quicker than team-mate Nico Hulkenberg, with McLaren’s Carlos Sainz eighth.
Red Bull’s Max Verstappen, Toro Rosso’s Daniil Kvyat and McLaren’s Carlos Sainz will start the race from the back as a result of penalties for using too many engines.
And Raikkonen, although he was classified 10th, is likely to join them, as it seems inconceivable he will not at least have to have a new gearbox after smashing backwards into the barriers, which would mean a five-place penalty. And depending on any other changes Alfa make to the car, there may be more.