Ferrari's former Formula One world champion Fernando Alonso upstaged the mighty Mercedes team by setting the pace in first practice for the Canadian Grand Prix.
Alonso, a winner on the Circuit Gilles Villeneuve in 2006 and runner-up to world champion Sebastian Vettel last year, lapped the island track with a best time of one minute 17.238 seconds on an overcast morning on the banks of the St. Lawrence river.
Right behind the Spaniard were the Mercedes due of Lewis Hamilton, a three-times winner in Canada, and his team mate and championship leader Nico Rosberg.
The Briton and German arrived in Canada downplaying a spat between the team mates that had dominated talk up and down the paddock but on the track their rivalry remained firmly in place.
Hamilton, who had his four-race win streak snapped by Rosberg in Monaco, was just 0.016 behind Alonso followed closely by Rosberg.
With six wins from six races Mercedes have ruled the Formula One grid and are expected to continue their domination on a Montreal circuit that plays to the car's strengths with high- speed straights.
Red Bull continued to improve with Vettel fourth on the timesheets ahead of Valtteri Bottas of Williams and Australian Daniel Ricciardo in the second Red Bull.
McLaren's Jenson Button, who claimed victory in a rain- soaked 2011 Canadian Grand Prix, was seventh best followed by team mate Kevin Magnussen.