Dutch cyclist Koen Bouwman has claimed a first Grand Tour stage victory after winning a tough seventh stage of the Giro d'Italia as Spain's Juan Pedro Lopez kept hold of the leader's pink jersey.

Bouwman was given a great lead-out by Team Jumbo-Visma teammate, 2017 Giro winner Tom Dumoulin, and sprinted to the line to edge out Bauke Mollema and Davide Formolo by two seconds as the Giro tackled its first mountain range, the Apennines, on Friday.

It was only a second ever victory for Bouwman, who won a stage in the Criterium du Dauphine in 2017.

"Unbelievable, like my first victory in the Dauphine, I can't believe it," he said.

"It was such a hard day actually, and in the final we were four guys with two of us, and Tom did a superb job in the last 2k."

Bouwman had time to look behind and raise his arms over his head as he crossed the finish line of the 196-kilometre route from Diamante to Potenza that included four categorised climbs and almost no flat sections.

All four had been part of a seven-man breakaway that managed to get away on the second categorised climb, the top classified ascent up Monte Sirino.

Most of the overall contenders crossed the line together, nearly three minutes behind Bouwman, with no change to the general classification.

Lopez maintained his 38-second advantage over Lennard Kamna after moving into the overall lead on Tuesday, with Rein Taaramae third, 58 seconds behind the Spaniard.

The leading Australian remains INEOS Grenadiers' Richie Porte in ninth overall 2:04 behind, with Jai Hindley (Bora-Hansgrohe) 14th at 2:16 down, and Lucas Hamilton (Team BikeExchange-Jayco) 19th at 2:27.

Saturday's eighth stage sees the Giro return to Naples for the first time since 2013 when the city hosted the start of the race.

The undulating 153-kilometre stage starts and finishes in the city but takes in four laps of a 19-kilometre circuit in the volcanic surrounding area.