By Alan Baldwin
SPIELBERG, Austria (Reuters) - World champions Mercedes dominated first practice for the Austrian Grand Prix on Friday with Formula One leader Nico Rosberg lapping faster than ever around the scenic Red Bull Ring.
The German's best lap of one minute 07.373 seconds on a bright but cloudy morning was 0.357 quicker than team mate and triple world champion Lewis Hamilton.
Ferrari's Sebastian Vettel, who is likely to collect a five-place grid penalty in Sunday's race for an unscheduled gearbox change, was third on the timesheets in 1:08.022 with team mate Kimi Raikkonen fourth.
Red Bull's Daniel Ricciardo, celebrating his 27th birthday, was fifth fastest.
Rosberg, who leads Hamilton by 24 points after eight of 21 races, is the only driver on the current grid to have won in Austria after victories in the past two years. The track returned in 2014 following an 11-year absence.
His fastest lap on Friday, using the quickest ultrasoft tires on a resurfaced track, compared to the 2015 pole position of 1:08.455 and the race lap record of 1:08.337 set by compatriot Michael Schumacher for Ferrari in 2003.
It was also three seconds quicker than his own fastest lap of 1:10.401 in first practice last year.
While Rosberg had a clean session, Hamilton spun into the gravel and triggered the virtual safety car at turn eight. Frenchman Romain Grosjean, in the Haas, also spun off as he avoided the Mercedes.
The circuit's revised kerbs also caused problems for Red Bull's Max Verstappen, who called them 'unbelievable' and 'dangerous' after two incidents.
The Dutch 18-year-old ended up in the gravel half an hour before the end of the session with a damaged suspension after earlier smashing his car's front wing on the kerb at the penultimate corner.
"The yellow kerbs in the fast corners are really dangerous," he said over the car radio.
The new kerbs have been introduced to force drivers to respect the track limits.
Rain could hit the afternoon session after thunderstorms lashed the circuit, set against a backdrop of the forested Styrian mountains, on Thursday.
(Editing by John O'Brien)