MONACO - After crashes, engine problems and eight races without a win, Lewis Hamilton's jubilation was evident as he threw himself into the arms of his Mercedes team after winning Sunday's rainy, incident-packed Monaco Grand Prix.

Mercedes F1 driver Lewis Hamilton celebrates on the podium after winning.[Photo/Agencies]??

Despondent Red Bull driver Daniel Ricciardo started from pole position and finished second - after a blunder from his team which failed to have his tires ready - and Mexican driver Sergio Perez was third for Force India.

Hamilton's victory was even sweeter because he closed the gap on championship leader Nico Rosberg, his teammate, who finished a lowly seventh after obeying orders to let Hamilton pass early on.

Hamilton's mood was in stark contrast to Saturday evening when - after qualifying in third place - he wrote off his chances of victory on a track so difficult to overtake on.

"I went to have a beer with some friends," Hamilton said, explaining how he snapped out of his torpor. "In the past, I would have been (angry) all night long ... I would have denied myself some of the other great things about this place."

After his win, Hamilton was in the mood to hug everyone - including catering staff in the team motorhome - having also received warm praise from Canadian pop star Justin Bieber shortly after taking the checkered flag.

Two weeks ago, Hamilton and Rosberg crashed into each other at the Spanish GP, both going out of the race and failing to pick up points.

This time, the struggling Rosberg moved aside to give Hamilton a chance to catch Ricciardo and clinch his 44th career win - the same number on Hamilton's current car and when racing karts in his younger days.

"It's such a special number for me and my family," said Hamilton, who thanked his mechanics. "(They) have been tense all (season) long. Today must be a great relief for them."

Hamilton's only other Monaco win was in 2008 for McLaren.

"As soon as it rained I knew there was an opportunity," Hamilton said. "Fortunately I was quick enough in the wet."

Hamilton closed the championship gap on Rosberg to 24 points, while Ricciardo is in third spot.

Because of poor visibility and a drenched circuit, the first few laps were behind a safety car.

But once the racing began properly, it was a thriller featuring multiple crashes and the comical sight of Red Bull's pit crew not being ready for Ricciardo's tire change.

The Australian driver was unforgiving, saying "everyone was running around like headless chooks (chickens)."

By contrast, Hamilton - who had not won since clinching last season's United States Grand Prix - was delighted, grabbing the race trophy from Monaco's Prince Albert and tossing it up in the air.

Winner of seven of the past eight races, including the first four this season, Rosberg's awful day was compounded when he was overtaken at the line by Nico Hulkenberg.

Mercedes head of motorsport Toto Wolff confirmed Rosberg had received team orders to let Hamilton through.

After the track dried out, Hamilton came in for quicker ultra-soft tires on lap 32, with Ricciardo coming in a lap later to switch to the same tires.

But in an astonishing oversight, Red Bull's crew was not ready.

''Two races in a row I've been screwed,'' said Ricciardo, whose team made an error when he finished fourth in Spain two weeks ago. ''They should have been ready. It hurts.''

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Five laps later, however, Ricciardo went close to overtaking Hamilton.

But Hamilton held his line at the Mirabeau turn, prompting an angry reaction from Ricciardo, who waved his right hand furiously.

''I forced him into the fence and by doing so he made a mistake and cut across the chicane,'' Ricciardo said. ''Obviously it was a chance to get the lead, so sure I questioned it.''

Perez was delighted with his seventh career podium, because ''in these conditions it's one of my best races.''

Ferrari driver Sebastian Vettel was fourth, ahead of McLaren's Fernando Alonso and Hulkenberg, who is Perez' teammate.

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Ferrari's Kimi Raikkonen and Red Bull's Max Verstappen were among seven drivers who failed to finish.

Toro Rosso's Daniil Kvyat - the Russian driver twice blamed for racing incidents with Vettel this season - ploughed into the turn at La Rascasse, taking Kevin Magnussen's Renault into the barriers with him.

Earlier, British driver Jolyon Palmer, Magnussen's teammate, had crashed when the track was soaked.

Sauber teammates Felipe Nasr and Marcus Ericsson collided amid some confusion over team orders.