Marc Marquez emerged as top dog in second practice for Moto GP's Grand Prix of the Americas, on a day when a mischievous canine interrupted proceedings in Texas.

Friday's opening practice session was brought to a halt in bizarre circumstances when a dog ran on to the circuit - forcing marshals to bring out red flags.

Following a brief pause, it was Ducati's Andrea Dovizioso who ended FP1 with the lead, courtesy of a time of 2:19.402 in wet conditions.

Yet Repsol Honda rider Marquez - the victor in each of the two previous editions of this event - laid down a marker in session two, topping the timesheets with a mark of 2:04.835.

The reigning world champion finished 0.327 seconds ahead of Cal Crutchlow (CWM LCR Honda), with Andrea Iannone (Ducati) rounding out the top three.

Dovizioso had to settle for fifth place in FP2, behind Aleix Espargaro, with Valentino Rossi - winner of the season-opener in Qatar - sixth.