MONACO (Reuters) - Australian Daniel Ricciardo set the pace for Red Bull in Monaco Grand Prix practice on Thursday, with crashes and a loose drain cover putting safety back in the spotlight at Formula One's showcase race.
Ricciardo lapped the twisty harbourside circuit in a quickest time of one minute 14.607 seconds, 0.606 faster than triple champion Lewis Hamilton in the closest Mercedes with championship leader Nico Rosberg third.
"Come qualifying and race day Mercedes will turn it up but hopefully I can stay in front," said the Australian.
Hamilton was fastest in the morning with a lap of 1:15.537 on the new ultrasoft Pirelli tyres making their debut this week.
The Briton, who collided with Rosberg in Spain 11 days ago and lags the German by 43 points after five races, is seeking to end his team mate's run of three successive Monaco wins but Ricciardo could be a threat to both.
"Generally it's been a really positive start. We've got everything we needed done in both sessions and our pace looks good, so hopefully that continues through the rest of the weekend," said Hamilton.
Red Bull had targeted Monaco as their best chance of victory this season, before Dutch teenager Max Verstappen won in Spain on his debut for the team.
Ricciardo has a new specification Renault engine for Sunday's race, which Verstappen will not get until the next race in Canada due to a shortage of parts.
"The engine has helped a little bit but obviously we have a good car around here as well, I think it’s down to a little bit of both," said Ricciardo of his time.
Verstappen was fifth and fourth in the respective sessions.
Ferrari's Sebastian Vettel, who spun at Mirabeau and hit the barrier after lunch, had been third fastest in the morning but four tenths slower than Hamilton.
With the paddock rocked by news that the family of the late French driver Jules Bianchi were taking legal action against Formula One, his former Marussia team and the governing FIA after his death last year, safety was a talking point.
A series of crashes led to the virtual safety car being deployed three times in the morning before the session was stopped when a loose drain cover damaged Rosberg's car and Jenson Button's McLaren. Photographs showed a sizeable piece of metal had been dislodged, fortunately without consequences for Button or anyone following behind.
Track workers were deployed to Sainte Devote to weld down the offending cover.
"That was an incident we definitely don't want to see again around here," Button said. [L3N18N4IZ].
Brazilian Felipe Massa, who was hit on the head and seriously injured by bouncing debris at the 2009 Hungarian Grand Prix, crashed out earlier when he skewed his Williams into the barriers at the first Sainte Devote corner.
Mexican Esteban Gutierrez stopped his Haas before Portier with electrical problems, and Renault's British rookie Jolyon Palmer crashed at Tabac.
"Sorry guys," Palmer, whose Danish team mate Kevin Magnussen also crashed in the afternoon, said over the radio.
Indonesian rookie Rio Haryanto crashed his Manor in the second session at the tunnel exit.
Editing by Amlan Chakraborty and Ed Osmond