Ferrari driver Fernando Alonso set the fastest time in Saturday's final practice session for the Singapore Grand Prix, with Red Bull's Daniel Ricciardo second.

The pace of the Ferraris and Red Bulls suggested they could challenge the Mercedes drivers — who have taken all but one pole position this season — in qualifying at Marina Bay later in the evening.

Mercedes' Nico Rosberg was third fastest and his teammate and championship rival Lewis Hamilton was sixth, separated by Toro Rosso's Jean-Eric Vergne and Red Bull's Sebastian Vettel, who has won the past three races in Singapore.

There was improvement from the Williams drivers, who were well off the pace on Friday. Felipe Massa was seventh, ahead of teammate Valtteri Bottas.