Lewis Hamilton's Mercedes broke down on day two of Formula One pre-season testing in Barcelona.

The six-time F1 world champion's W11 ground to a halt during the afternoon session at Circuit de Barcelona-Catalunya on Thursday.

Hamilton had to wait at the side of the track as the red flags were waved before his car was taken back to the garage.

Mercedes tweeted: "W11 is back in the garage. The team will now take a look to identify the issue which caused Lewis to stop on track."

The team later revealed Hamilton's car was troubled by "an oil pressure anomaly".

"@LewisHamilton stopped on track due to an oil pressure anomaly, which made the engine shut down as a precautionary measure," Mercedes said on Twitter.

"We will keep investigating further but unfortunately that concludes our running for the day."

The malfunction occurred just a fortnight before Hamilton starts the defence of his title at the Australian Grand Prix.

Ferrari's Sebastian Vettel topped the leaderboard in the morning session after spinning into the gravel, while Red Bull driver Max Verstappen spun twice.

Hamilton was seventh-fastest on day one of testing after clocking up 89 laps.