Charles Leclerc edged team-mate Sebastian Vettel on Saturday morning as Ferrari registered another one-two in an incident-filled practice session in Spa in which championship leader Lewis Hamilton crashed into a wall.
Leclerc, who was fastest in second practice on Friday afternoon after Vettel had topped the times in the morning, clocked a best lap in one minute and 44.206 seconds to finish ahead by 0.451 seconds.
Valtteri Bottas was third fastest for Mercedes, almost half a second off the leading pace, while his team-mate Hamilton wound up seventh having crashed heavily to prompt a 13-minute red flag stoppage midway through the action.
The Briton lost control and smashed into the barriers in a high-speed collision at Les Fagnes where he appeared to run over a kerb before bouncing across a run-off area.
Hamilton was unhurt but his car appeared seriously damaged. Mercedes, though, were confident it would be fixed in time for qualifying.
“We will be replacing both front corners (suspension and wheel assemblies), nose, barge boards and floor on Lewis’ car,” the team tweeted.
“Barring any unexpected surprises, we believe we can complete all of the work in time for the start of #BelgianGP qualifying!”
Daniel Ricciardo was fourth for Renault ahead of Red Bull’s Max Verstappen, who was backed by a vast ‘orange army’ of Dutch fans who have packed into the campsites around the circuit this weekend.
Sergio Perez was sixth for Racing Point, 24 hours after signing a new-three-year deal to stay with the team, ahead of Hamilton, the Alfa Romeos of Kimi Raikkonen and Antonio Giovinazzi, and Pierre Gasly, back with Toro Rosso after being dropped by Red Bull.
His replacement in the senior team, London-born Thai rookie Alex Albon, spent the session evaluating a new rear wing for his car rather than seeking a fast one-lap pace because he is due to start from the back of the grid. He was 20th.
Qualifying starts at 1300GMT.