Riding for Bora–Hansgrohe, the 25-year-old snatched victory at the finish line in a tense affair in this International Cycling Union WorldTour event. 

McCarthy was trapped in the peloton going into the final two kilometres of the 184.8km stage from Bermeo to Villanueva de Valdegovia.

It had looked like Alex Aranburu, riding for Caja Rural, was going to win as he broke away from the pack and sprinted towards the finish line.

The Spaniard, however, could not keep up his effort and was sucked back into the peloton with just 500 metres to go.

Even with such a short distance left, nobody looked like they would be making a break on their own for the finish line, meaning the riders had to push hard and hope for the best.

It was McCarthy who pipped his rivals to the line, securing victory in a time of 4 hours 49min 39sec.

Belarus' Aleksandr Riabushenko and Poland's Michal Kwiatkowski, riding for UAE Team Emirates and Team Sky respectively, finished in second and third place.

The Tour of the Basque Country is still led by Quick-Step Floors rider Julian Alaphilippe of France, who finished sixth today and has an overall time of 13:18:52 - eight seconds ahead of Slovenia's LottoNL-Jumbo rider Primož Roglič - after winning the opening two stages of the event.

Stage four of the competition takes place tomorrow in the form of a 19.4km individual time trial in Lodosa.

The Tour of the Basque Country is due to conclude on Saturday (April 7).