MONACO (AFP) - Briton Lewis Hamilton topped the times for Mercedes ahead of Red Bull's Max Verstappen in Thursday morning's (May 23) opening free practice session at Formula One's Monaco Grand Prix.

In a sombre atmosphere following the death of three-time champion Niki Lauda, the championship leader and five-time champion clocked a fastest lap of the famous Mediterranean street circuit in 1 min 12.106sec to outpace the Dutchman by 0.059 of a second.

Hamilton's Silver Arrows team-mate Valtteri Bottas was third, only 0.072sec adrift of the Englishman, and ahead of Monegasque Charles Leclerc of Ferrari and his teammate Sebastian Vettel and Pierre Gasly in the second Red Bull.

The two Ferraris were three-tenths and seven-tenths slower than Hamilton respectively. It was the first time a Mercedes car had led a Monaco session since 2017, boosting their hopes of extending their dominant season-opening streak of an unprecedented five one-two triumphs.

The session began in the midst of poignant tributes to Lauda, including a solitary red baseball cap left hanging on his earphones peg, were all around the Mercedes team motorhome and their cars.

On a dry and hazy morning in the principality, the cramped harbourside paddock was in sombre mood as Formula One honoured the Austrian, who died on Monday aged 70.

Like Mercedes, where he was a larger-than-life figure on the pit wall as the team's plain-speaking non-executive chairman, and Ferrari, with whom he won his first two championships, McLaren were also honouring the memory of the man and where he won his third drivers' world title.

The Ferrari SF90s ran with a decal marking his time with them in the form of a replica graphic of his name as used on the side of the cars when he raced for the team from 1974 to 1977. It was underlined in black as a sign of mourning.

Sebastian Vettel, the four-time champion who is a keen historian of the sport and was close to Lauda, wore a special helmet livery reflecting the famous red one the Austrian used in his racing career.

Mercedes marked the passing of the man who was instrumental in persuading Lewis Hamilton to join from McLaren with a red star, Lauda's signature and a message of thanks "Danke Niki" on their cars.

"As you can imagine, this is a very difficult time for the team, for all of us, and it is very difficult, most importantly, as a friend," said team boss and fellow Austrian Toto Wolff.

"It's not an easy situation to try to go back to racing especially not in Monaco with so much media attention.

Losing an icon, and a friend

"I am trying to keep it together emotionally in speaking about a friend. This is what matters most and what hurts the most. It is one thing that the world and the F1 community has lost the biggest icon, but it is totally different, and more difficult, to have lost a friend."

Vettel not only sported a near-replica Lauda helmet, but revealed also that, after learning of his friend's lung transplant operation last year, he wrote a letter that he described as being "a great pleasure" and "full of fine words."

In practice, Nico Hulkenberg was seventh for Renault ahead of Kevin Magnussen of Haas, Kimi Raikkonen of Alfa Romeo, who is due to start his 300th race on Sunday, and Romain Grosjean, in the second Haas.

The two Haas cars missed much of the session after being black-flagged to return to the pit lane due to communication problems that were resolved, permitting them to rejoin the action.

Carlos Sainz of McLaren was unable to clock a lap time after suffering technical problems with his car.