Davide Bais won a gruelling stage seven of the Giro d'Italia after leading a three-man breakaway, beating Karel Vacek and Simone Petilli to the finish line for his first professional victory.

Friday's seventh stage was one for the climbers on a 218km ride from Capua to Gran Sasso d'Italia.

It involved flat roads at the start before the final climb of approximately 45km and a total altitude gain of 3,900 metres.

The breakaway trio were seven-and-a-half minutes ahead of the peloton with 20km to go and showed no signs of slowing down.

As they pedalled up an unrelenting climb through snow-banked roads, Czech rider Vacek fell away and looked to be out of the contest. But he put his head down and caught up with the two Italians again in the final two kilometres.

They waited for each other to take charge in the final kilometre but it was 25-year-old Eolo-Kometa rider Bais who found a reserve of energy to surge ahead.

He dropped his rivals and sprinted ahead in the last 200 metres to take victory as Italian fans around the finish line roared their approval.

Vacek finished second while Petilli was third after the pair ran out of steam.

"Finally, my first pro win has arrived. It was unexpected because I went into the breakaway to prepare for an attack by (teammate) Lorenzo Fortunato," Bais said.

"He was the inspiration for our team to go for a mountain stage victory since he made it at Monte Zoncolan two years ago.

"In the finale I knew I was the fastest so I waited for my time to come to do the last effort."

Andreas Leknessund of Team DSM retained the leader's maglia rosa jersey with a 28-second lead over Remco Evenepoel.

The Belgian led the sprint involving the general classification riders that finished three minutes and 10 seconds behind Bais.

He was joined by another pre-race favourite, Primoz Roglic, with no change in the general classification as the contenders opted not to attack with a headwind making things difficult on the mountain.

Leknessund could hold on to the maglia rosa on Saturday but the Norwegian's lead will be put to the test in Sunday's time trial.