Lewis Hamilton again topped the timesheet in practice ahead of the Monaco Grand Prix, but the rain-affected second session put a dampener on things for Formula One fans.

Fresh from signing a lucrative three-year deal with Mercedes on Wednesday, the 30-year-old spoke of his desire to achieve a "perfect weekend" in the Principality.

Things certainly look promising for Hamilton, who bettered his quickest time of the first free practice session with a best lap of one minute 17.192 seconds later in the day.

No driver managed more than 10 laps before the red flag was raised in Monaco after Manor's Roberto Merhi crashed into the wall, losing his front wing after coming out of the tunnel.

The incident coincided with a turn in the weather, with rain meaning the remaining 19 cars returned to the garage.

Lotus' Pastor Maldonado tip-toed back out on to the track on supersoft tyres, but quickly returned after saying it was "raining too much".

Teams were reluctant to follow given no rain is forecast for Saturday and Sunday, leading to a number of fans jeering in frustration.

Fernando Alonso eventually made his way out with just over 10 minutes remaining but the McLaren driver, like the rest of the grid, had no choice but to take it easy.

Unsurprisingly, nobody managed to post a better lap during that run so the standings stayed as they were when the red flag came down.

Nico Rosberg finished ninth in the first practice session but improved this afternoon by finishing second, 0.740secs behind team-mate Hamilton.

Ferrari duo Sebastian Vettel and Kimi Raikkonen followed them, with Daniil Kvyat of Red Bull and the Toro Rosso pair of Carlos Sainz Jr and Max Verstappen the next quickest.

McLaren's Alonso finished eighth in the second session and Force India's Nico Hulkenberg and Sergio Perez closed out the top 10.

Williams' Felipe Massa and Valtteri Bottas placed before Maldonado and Jenson Button, who endured a tough first session after his McLaren was only able to enter the fray after a 50-minute mechanical delay.

Daniel Ricciardo and Felipe Nasr of Red Bull and Sauber, respectively, followed in the second session, with Manor's Merhi and Will Stevens finishing 18th and 19th. Marcus Ericsson of Sauber did not get out of the pits due to a technical issue.

The morning session certainly was a more interesting spectacle, with Toro Rosso's Verstappen the main talking point.

A fine finish to the Dutchman's first ever session around Monaco saw him secure the second fastest lap, just 0.149secs behind Hamilton. Ricciardo of Red Bull finished third.