Tim Wellens claims victory in the fourth stage of the Giro d'Italia ©Getty Images

Belgium's Tim Wellens won the gruelling fourth stage of the Giro d'Italia, but Australia's Rohan Dennis still maintains the narrowest of overall leads.

The 202 kilometre ride from Catania to Caltagirone, ending with a steep finish, proved troublesome for Britain's Chris Froome.

The four-times Tour de France winner, under investigation for an adverse doping test in last year's Vuelta, lost 23 seconds in the later stages.

The Giro reached Italian soil in Sicily after three days in Israel and a rest day, and Wellens was tipped as a favourite for the stage.

The Lotto-Soudal rider went with a late break and sustained his effort on an 800 metre climb up an average gradient of almost 10 per cent to the finish line, which he crossed in 5 hours 17min 34sec.

Rohan Dennis of Australia still leads the overall standings in the Giro d'Italia after the fourth stage - by one second ©Getty Images
Rohan Dennis of Australia still leads the overall standings in the Giro d'Italia after the fourth stage - by one second ©Getty Images

Canada’s Michael Woods and Italy’s Enrico Bataglin were second and third respectively, and given the same time.

Dennis, riding for BMC, retained the overall leader's pink jersey with a time of 14:23.08, one second faster than the defending champion Tom Dumoulin of The Netherlands.

Simon Yates is third overall, 17 seconds adrift, with Wellens two seconds further back.

"Of course I want to stay in the front," Dennis said.

"It's great to keep the jersey for a little bit longer, the team did everything possible to put me in that position.

"It was a little bit stressed, but not so much."

Portgual's José Goncalves, one of the overall contenders, suffered mechanical problems and dropped out of the top 10.