Red Bull driver Max Verstappen finished fastest in practice for the Monaco Grand Prix as Ferrari's Carlos Sainz crashed out.
Verstappen edged out home favourite Charles Leclerc by just 0.065 seconds with his Ferrari team-mate Sainz third.
Fernando Alonso finished fourth for Aston Martin ahead of McLaren's Lando Norris and Mercedes' Lewis Hamilton.
As Verstappen raced to the top of the charts, Sainz's running ended with 17 minutes remaining.
The Spaniard, who was earlier quickest in the first session, clipped the entry barrier into the swimming pool chicane, damaging his right-front suspension, before heading straight into the tyre wall on the opposite side of the track.
"I crashed," said the Spaniard. "I'm sorry." The session was suspended for six minutes as Sainz's wounded Ferrari was removed from the circuit.
After giving up on this season's car on the eve of the opening race, Mercedes have arrived for the sixth round in the sun-cooked principality with a new concept.
The Silver Arrows have abandoned their controversial zero-sidepod design and introduced a new front suspension, new floor and cooling system in a change of development on a car which has contributed to the longest losing streak of Hamilton's career.
On Sunday, it will be 539 days since Hamilton last stood on the top step of the podium at the penultimate round of the contentious 2021 season in Saudi Arabia.
However, on the evidence of practice, the seven-time world champion appears no closer to the front.
Hamilton ended the opening running in third place, but he had dropped to sixth by the conclusion of the day, half-a-second back. George Russell was a disappointing 12th in the other Mercedes, seven tenths adrift.
Verstappen and team-mate Sergio Perez are the only men to have won a race this year and their rapid Red Bull is not necessarily suited to the narrow and slow-speed confines of the unique Monte Carlo configuration.
But, despite Perez managing only seventh in practice, Verstappen's pace on Friday suggests he might yet be the driver to beat for the remainder of the weekend.
In first practice, the red flags were deployed in the closing minutes when Alex Albon lost control of his Williams through the opening Sainte Devote corner.
The London-born Thai slammed into the wall, but, despite admitting to banging his knees, he emerged relatively unscathed from the 100mph accident.
The same could however not be said for Albon's Williams following significant damage to the left-hand side of his machine.
He returned to the track with 11 minutes of second practice remaining following a three-hour repair job by his team.
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