Ferrari's Fernando Alonso set the pace in the first practice for the Monaco Grand Prix here on Thursday as Heikki Kovalainen's Caterham blew up bringing a premature end to the session.
With ten minutes remaining of the hour-and-a-half practice around the streets of the Principality, the Renault engine of the Finn's car packed up as he went through the tunnel with clouds of smoke and oil on the track forcing an immediate red flag.
Spaniard Alonso clocked 1min 16.265sec, finishing 0.365sec faster than Romain Grosjean in a Lotus, with Mexican Sergio Perez of Sauber third fastest, 0.081 behind the Frenchman.
Two-time world champion Alonso, twice a Monaco winner, battled with Grosjean and Britain's Lewis Hamilton throughout the session which each led in turn.
McLaren's Hamilton, who won here in 2008 the year he went on to take the world title, was fourth fastest with 1:16.747.
Williams driver Pastor Maldonado, winner of the last race in Spain, was fifth, ahead of Ferrari's Felipe Massa, Sauber's Kamui Kobayashi, McLaren's Jenson Button, Red Bull's Sebastian Vettel and Mercedes driver Nico Rosberg.