A HALF-NAKED fan caused chaos at the Vuelta a Espana with several cyclists crashing during stage two.

One rider was left enraged after claiming he collided with a "drunk fan" in the hills of Portugal, with the race not reaching Spain until stage four on Tuesday.

Fans got carried away as they watched the peloton climb uphill with one fan sprinting wearing only his underwear.

Riders were given a narrow passage to squeeze through with excited fans on either side of the road cheering them on.

Seconds after the half-naked fan veered of course several riders fell.

Trek rider Mathias Vacek, who finished second in stage one and just two seconds off winner Brandon McNulty, was one of them.

He bemoaned his lack of luck on social media after crashing, claiming a drunk fan was to blame.

Vacek said: "Not my luckiest day today after crashing because of a drunk Fan ‍♂️

"But I managed to get safe to the finish with no serious injuries
Great job from the @lidltrek mates keeping everything under control "

Unfortunately for Vacek, there were just over four kilometres left in the stage which meant he was unable to launch an attack in a bid to overhaul the two-second deficit he had to race leader McNulty.

Instead, Wout van Aert took advantage of the chaos to claim the red jersey, and he now leads the race ahead of McNulty and Vacek, who make up the top three.

Brit Joshua Tarling is down in sixth, 11 seconds off the leader while one of the favorites to win overall, Primoz Roglic, is eighth.