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Title rivals Max Verstappen and Charles Leclerc will start the Belgian Grand Prix from the back of the grid.
The Red Bull and Ferrari stars are two of six drivers to be penalised for using too many engine parts.
Joining them are McLaren's Lando Norris, Alpine's Esteban Ocon, Valtteri Bottas of Alfa Romeo and Haas' Mick Schumacher.
Leclerc and Verstappen finished first practice second and third, behind the Ferrari of Carlos Sainz.
Mercedes driver George Russell was fourth.
It was a session truncated by a 12-minute red-flag period to recover the stranded Haas of Kevin Magnussen, after it broke down on the run between the opening La Source hairpin and the Eau Rouge sweepers.
Verstappen was comfortably faster than anyone else for much of the session, after running the soft tyres early on, before being overhauled by the Ferraris later on.
Sainz was just 0.069 seconds quicker than Leclerc, who was on course to go top before a slide at the final chicane.
Verstappen was 0.217secs off Sainz in third place, with Russell 0.858secs off the pace while trying a significant aerodynamic upgrade.
An inconclusive session ended with Aston Martin's Lance Stroll fifth from Williams' Alex Albon and Daniel Ricciardo, who it was announced this week will leave McLaren at the end of the season after the team reached a deal to terminate his contract.
Lewis Hamilton was ninth fastest, behind Alpha Tauri's Yuki Tsunoda, with Red Bull's Sergio Perez completing the top 10.