Sebastian Vettel leads Red Bull rampage in Singapore

Red Bull laid down an early marker for the Singapore Grand Prix when Sebastian Vettel stormed to the fastest time in second free practice on Friday, a few hours after team mate Mark Webber had led the way in the first.

Armed with an upgraded package, including a new rear wing, the German clocked one minute 46.660 seconds around the floodlit Marina Bay circuit, 0.627 seconds ahead of championship leader Webber and more than a second ahead of the rest.

Lapping in similar conditions expected for Sunday''s night race, times in the second session were far quicker than those clocked on the damp track earlier, with the title challengers all likely to take encouragement from their performances.

McLaren expect their cars to run well this weekend and world champion Jenson Button improved from the first session to finish just behind Webber, with team mate Lewis Hamilton fifth on the timesheets.

Wedged between the Britons was the Ferrari of Fernando Alonso, who continues to show good form in his late season surge for a third world title and was unlucky to stall his engine while on a very quick lap late in the session.

With five races remaining, the top five drivers are separated by only 24 points in the standings and the season-long tussle for the world title looks set to continue on a circuit that exaggerates the slightest of mistakes.

Force India's Adrian Sutil lost a front wheel after flipping over the kerbs of a chicane and Alonso was unable to restart his car after skidding into a runoff area when he lost control while challenging Vettel''s fastest time.

"This morning we wanted to do more mileage but the conditions could not make that possible," Ferrari team principal Stefano Domenicali told reporters.  

"The situation improved in the afternoon but it's difficult to judge where we are after Fernando had a slight problem when he was running quickly.  

"It's tough to know how fast we are compared to the others but we will try our best in qualifying."                                                     

Drying track                                      

Rubens Barrichello was best of the rest, taking an encouraging sixth for Williams ahead of Felipe Massa in the second Ferrari.  

Earlier, the first action of the weekend took place on a drying track following a mid-afternoon downpour with a majority of the teams waiting for conditions to improve before completing timed laps. 

Webber clocked one minute 54.589 seconds to edge out Michael Schumacher by 0.119 seconds as the seven-time world champion headed a trio of Germans around the tight and demanding course.

Sutil recorded a third fastest time of 1:54.827 while Vettel completed 12 laps of work in fourth place with a 1:55.137.              

"Unlike others, (Webber and Vettel) don't need to do a whole lot of laps around here to learn the track so we are just waiting for conditions to improve a little bit more," Red Bull team principal Christian Horner said in a television interview.                  

"I think all the teams have brought something a bit new here this weekend, we have done likewise.                                           

"It's going to be interesting to see how that pans out and the different challenges. This circuit is fairly unique... it's going to be fascinating to see whose cars and drivers suit this circuit."