Formula One world champion Sebastian Vettel took his fifth victory in six races when he won a crash-hit Monaco Grand Prix thriller for Red Bull on Sunday.

With the safety car twice deployed and the race red-flagged after 71 of the 78 laps due to a pile-up at the Swimming Pool complex, the 23-year-old German held on from the re-start for his first win in the principality.

Vettel now has a 58-point lead over McLaren's Lewis Hamilton, who scrambled to sixth place despite a drive-through penalty and numerous scrapes that triggered another stewards' investigation.

Ferrari's double world champion Fernando Alonso finished second and ahead of McLaren's 2009 winner Jenson Button in third, with the top three separated by just 2.3 seconds in a knife-edge chase to the line.

"You beauty, that was a champion's drive," team boss Christian Horner told Vettel over the radio as he took the chequered flag.

The race was red-flagged when Renault's Russian Vitaly Petrov slammed into the wall on lap 71 after Toro Rosso's Jaime Alguersuari and 2008 winner Hamilton had tangled ahead of him as the leading trio came through.

While marshals cleared up the debris, an ambulance and doctors tended to Petrov.

"Vitaly is okay. He's just complaining about leg injuries, but the doctors say nothing is broken. They are taking him to hospital for observation but it seems to be just bruising to the legs," team boss Eric Boullier told the BBC.

After a 21-minute delay, the race re-started behind the safety car.

Before the red flag, the top three had been separated by just 0.6 of a second with Alonso vainly seeking a way past the Red Bull as they skimmed the metal barriers with Button right behind the Spaniard.

The German, who had started on pole, made one stop to Alonso's two and Button's three.

There was more drama after the re-start when Venezuelan Pastor Maldonado, in sixth place and heading for Williams' first points of the season, tangled with Hamilton and spun into the barriers.

Hamilton was in the thick of the action throughout a sunny afternoon, collecting his drive-through for a collision at the hairpin with Ferrari's Felipe Massa, who then crashed out in the tunnel as Hamilton swept past.

Vettel's Australian teammate Mark Webber, last year's winner, was fourth with Sauber's Japanese Kamui Kobayashi fifth.

However stewards said Kobayashi, whose Mexican teammate Sergio Perez missed the race after crashing in qualifying, and Force India's Adrian Sutil, who finished seventh, were both under investigation for an incident.

While Williams missed out on a handful of points from Maldonado, his Brazilian teammate Rubens Barrichello delivered in ninth place to open the former champions' account for the season.