Ferrari driver Kimi Raikkonen set the pace in the opening practice session for the Russian Grand Prix on Friday.
Raikkonen posted a best lap of one minute and 36.074 seconds at the Sochi Autodrom to finish fractionally ahead of his Finnish countryman Valtteri Bottas.
Lewis Hamilton was third, more than half-a-second adrift of Raikkonen, while championship leader Sebastian Vettel finished the 90-minute session in fifth.
Vettel, who heads Hamilton by seven points following victories at two of the opening three rounds, was more than a second adrift of his Ferrari team-mate.
The four-time champion endured a moment of drama at turn 16 after he lost the back end of his Ferrari and faced the wrong way on the track before recovering to the sanctuary of his garage. He also made an error at turn 13 during an earlier run.
It was not the cleanest of sessions for Vettel's title rival Hamilton either as he bids to bounce back from his defeat at the last round in Bahrain.
The triple world champion, 32, ran over the kerbs at turn two before later running wide at the exit of turn 14. He will be hoping for an improvement in the second session which takes place later this afternoon.
Max Verstappen finished fourth for Red Bull with his team-mate Daniel Ricciardo sixth in the order.
Fernando Alonso, who arrived in Sochi directly from America following a seat fitting ahead of his Indianapolis 500 appearance next month, was 13th in the order.
But there were further problems for his McLaren team-mate Stoffel Vandoorne who reported a lack of power from his Honda engine in the closing moments of the action.
The session was also temporarily red-flagged after a large piece of pink bodywork bizarrely flew off of Esteban Ocon's Force India. A track marshal recovered the debris, while Ocon recovered back to the pits before the action resumed.
Sergio Perez, Felipe Massa, Lance Stroll and Ocon rounded out the top 10. British driver Jolyon Palmer, in need of a good result here following a difficult start to the new season, was 15th.
First practice times:
1 Kimi Raikkonen (Fin) Ferrari 1min 36.074secs
2 Valtteri Bottas (Fin) Mercedes GP 1:36.119
3 Lewis Hamilton (Gbr) Mercedes GP 1:36.681
4 Max Verstappen (Ned) Red Bull 1:37.174
5 Sebastian Vettel (Ger) Ferrari 1:37.230
6 Daniel Ricciardo (Aus) Red Bull 1:37.290
7 Sergio Perez (Mex) Force India 1:37.457
8 Felipe Massa (Bra) Williams 1:37.900
9 Lance Stroll (Can) Williams 1:37.944
10 Esteban Ocon (Fra) Force India 1:38.065
11 Daniil Kvyat (Rus) Scuderia Toro Rosso 1:38.496
12 Kevin Magnussen (Den) Haas F1 1:38.747
13 Fernando Alonso (Swe) McLaren 1:38.813
14 Carlos Sainz (Spa) Scuderia Toro Rosso 1:38.976
15 Jolyon Palmer (Gbr) Renault 1:39.158
16 Romain Grosjean (Fra) Haas F1 1:39.533
17 Stoffel Vandoorne (Bel) McLaren 1:39.541
18 Pascal Wehrlein (Ger) Sauber-Ferrari 1:39.731
19 Marcus Ericsson (Swe) Sauber-Ferrari 1:40.465
20 Sergey Sirotkin (Rus) Renault No Time