Max Verstappen led a Red Bull one-two from Daniel Ricciardo following a topsy-turvy opening practice session for Sunday's Azerbaijan Grand Prix.
Championship leader Sebastian Vettel finished third at the Baku Street Circuit, while Lewis Hamilton, who trails the Ferrari driver by 12 points in the title race, was only fifth.
Hamilton, a winner last time out in Canada, failed to set a time on the super-soft tyre, the quickest of the three Pirelli compounds available here, after falling foul to Sergio Perez's crash and then traffic.
Mexican driver Perez became the day's first big victim of this narrow and twisty street circuit when he lost control of his Force India and crashed into the wall.
Perez harmed only his pride in the incident after he carried too much speed through the ultra-tight Turn 7 with the front right of his car thudding the barrier on entry to the corner.
But his Force India sustained significant damage in the incident, and the way in which Perez's right-rear tyre completely detached from the car and bounced along the track will be cause for concern too.
Perez's crash resulted in the session being delayed for more than 10 minutes as the circuit's marshals removed his stricken vehicle and cleared the track of debris.
It led to a chaotic conclusion as a number of drivers - including both Vettel and Hamilton - attempted to improve on their time.
Neither did, with Vettel half a second slower than Verstappen, and Hamilton one second off the pace. Perez finished fourth in the order despite his crash with Hamilton's Mercedes team-mate Valtteri Bottas sixth.
Double world champion Fernando Alonso will start Sunday's race from the back of the field after incurring a series of grid penalties following changes to his Honda engine.
And the 35-year-old Spaniard was comfortably off the pace, with his McLaren only 15th in the order, 3.8secs adrift of the leaders.
Honda have brought a number of updates to Azerbaijan, but Alonso was desperately sluggish in a straight line with the speed traps indicating he was 20 miles per hour slower than the fastest cars.
British driver Jolyon Palmer is under pressure to deliver his first points of the season, but he was only 18th on Friday morning.
The Renault driver, 26, was four seconds slower than Verstappen's best effort and an eye-watering 1.3secs adrift of team-mate Nico Hulkenberg, who has out-qualified the Englishman at every round of the campaign so far.
Source: PA
