Raikkonen pulled over to the side of the track with smoke coming from the back of his car in FP1, having been ordered by his team to slowly make his way back to the pits.

Ferrari later said it was a turbo problem that stopped him, and it changed the internal combustion engine, turbo and MGU-H on his car for FP2.

“We had a power unit issue with Kimi – it was quite obvious,” said Ferrari technical director Mattia Binotto.

“We changed it for the afternoon just as a precaution, it was important for us to make sure Kimi could run the afternoon trouble-free.

“What happened is still to be fully understood. We analysed all the parts and hopefully all the elements of the power unit can be used again once they are sorted out.”

Raikkonen, who was-fourth fastest in FP2, played down the significance of the problem in the first session.

“It was nothing to do with the engine, it was some control issue with the turbo,” he said.

“It stopped us in the early part of practice so the guys did a good job to fix the car and be ready for second practice.

“It could have been better but that’s how it goes.”

Electrical problem halts Vettel

Ferrari appeared to be in more trouble in FP2 when Vettel’s car shut down in the same area of the track where Raikkonen had stopped in the first session.

However, the German was able to coast the car back to the pits after leaning forward to reach the "neutral" button ahead of the cockpit, and he rejoined the action shortly afterwards.

Binotto described it as “a minor electrical problem” and said Ferrari was “not too worried” about it.

Vettel, who topped both Friday sessions, added: “It must have been some sort of glitch, all of a sudden everything was dark.

“As we saw after there was no damage – we were lucky that we could recover with the issue happening late in the lap.

“Nowadays cars are not just cars, there’s also a lot of technology and software involved, so obviously something went wrong on that side.”

Additional reporting by Jonathan Noble