Alonso set a time of 1min49.056, followed by the Mercedes duo of Lewis Hamilton (1min49.178) and Nico Rosberg (1min49.205). The Red Bull pair of Sebastian Vettel (1min49.874) and Daniel Ricciardo (1min50.122) were fourth and fifth fastest.
Alonso's teammate, Kimi Raikkonen, also put in a competitive showing with seventh place, behind Toro Rosso's Jean-Eric Vergne, who performed strongly before his car suffered an electronics failure that briefly saw him block the pit exit.
WILLIAMS UNCOMPETITIVE?
McLaren's Jenson Button also had technical difficulties that restricted his running but was eighth fastest, followed by Toro Rosso's Daniil Kvyat and Force India's Sergio Perez.
The Williams cars were surprisingly uncompetitive. While this twisty circuit was expected to count against a team that thrived on the flowing Belgian and Italian tracks in the previous two races, it was still surprising to see Felipe Massa down in the 13th and Valtteri Bottas in 15th.
It was the first session run under the new restrictions on pit-car radio transmissions.
While the FIA relented on Friday (Sept 19) and delayed until 2015 a ban on radio messages about car performance, they did retain a ban on driver coaching - instructions on braking points, gear selection, car set-up at various points on the circuit, etc.
However old habits die hard, and Rosberg and Hamilton were heard asking their team about other drivers' tires and performance - banned under the new regulations - and received curt replies from the garage.
When Hamilton inquired as to the wear rate on rivals' tires, the radio message in reply was: "Just carry on with our program and we'll discuss it in the garage."
The opening 90-minute session was free of any major incident, with all but McLaren's Kevin Magnussen having driven the circuit before and learnt to adjust to its bumpy surface, long and technical layout, and close-in barriers.
First free-practice times ahead of the 2014 Singapore F1 GP
1 Fernando Alonso (Spain) Ferrari 1min49.056
2 Lewis Hamilton (Britain) Mercedes 1min49.178
3 Nico Rosberg (Germany) Mercedes 1min49.205
4 Sebastian Vettel (Germany) Red Bull 1min49.874
5 Daniel Ricciardo (Australia) Red Bull 1min50.122
6 Jean-Eric Vergne (France) Toro Rosso 1min50.539
7 Kimi Raikkonen (Finland) Ferrari 1min50.783
8 Jenson Button (Britain) McLaren 1min50.922
9 Daniil Kvyat (Russia) Toro Rosso 1min50.990
10 Sergio Perez (Mexico) Force India 1min51.131
11 Kevin Magnussen (Denmark) McLaren 1min51.217
12 Nico Hulkenberg (Germany) Force India 1min51.604
13 Felipe Massa (Brazil) Williams 1min51.953
14 Pastor Maldonado (Venezuela) Lotus 1min52.125
15 Valtteri Bottas (Finland) Williams1min52.146
16 Esteban Gutierrez (Mexico) Sauber 1min52.171
17 Adrian Sutil (Germany) Sauber 1min52.237
18 Romain Grosjean (France) Lotus 1min52.906
19 Jules Bianchi (France) Marussia 1min54.113
20 Marcus Ericsson (Sweden) Caterham 1min54.475
21 Kamui Kobayashi (Japan) Caterham 1min54.607
22 Max Chilton (Britain) Marussia 1min55.170
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