Ferrari's Charles Leclerc was fastest in a rain-shortened final practice Saturday for the Singapore Grand Prix, half a second quicker than championship leader Max Verstappen.

Heavy afternoon rain at the Marina Bay Circuit meant that only 30 minutes of running time was possible with Leclerc handling conditions the best as the track began to dry out, clocking 1min 57.782sec.

Verstappen's fastest effort in his Red Bull was 1:58.308 with the second Ferrari of Carlos Sainz third in 1:58.848.

Lewis Hamilton had sprung a surprise to be quickest in Friday's dry first practice, but struggled for grip on the intermediate rain tyres and was 12th, more than three seconds adrift of Leclerc.

Hamilton's Mercedes teammate George Russell was ninth quickest in a session that left more questions than answers just two hours before the all-important qualifying session under floodlights later on Saturday.

Single-lap pace in qualifying is crucial at Singapore, where pole position is a huge advantage on a tight track that affords few opportunities to overtake.

Spain's Fernando Alonso, who will start a record 350th grand prix on Sunday -- one more than Kimi Raikkonen's previous all-time mark -- was fourth fastest in his Alpine, 1.647sec slower than Leclerc.

Sergio Perez was fifth in the second Red Bull, Lance Stroll was sixth in the Aston Martin followed by Esteban Ocon's Alpine.

Sebastian Vettel, who won in Singapore for Ferrari the last time the race was run in 2019, was eighth in his Aston Martin.

Verstappen has an almost unassailable lead in the title chase but must win Sunday's race and see his closest rivals falter to retain his crown, or the fight will move on to Japan next week.