Frank kept hold of the leader's yellow jersey after finishing the 161-kilometre stage from Innertkirchen to Buochs safely in the peloton.

Sprint favourites Peter Sagan, the winner of Monday's third stage, and Tom Boonen were boxed in on a 90-degree bend 200-metres from the end and Demare surged through to take the victory from Australia's Matthew Goss with American Tyler Farrar in third.

"The whole team did great work for me even though it wasn't easy all day long with this hilly route," said the winner.

"In the last 25km I told myself I needed to recoup (energy) ahead of the sprint, knowing that there was great competition.

"I really am very happy to have succeeded against such good sprinters."
   
A three-man breakaway early in the day had got close to surviving right to the end of the lumpy stage that was made for a sprint finish, but the final escapee, veteran German break specialist Jens Voigt was caught inside the final five kilometres.

He had gone it alone after his companions Olivier Kaisen and Robert Vrecer fell by the wayside as their maximum lead of just over four minutes proved insufficient.

Sagan's Cannondale team and Boonen's Omega Pharma-QuickStep outfit led the chase towards the end of stage, ensuring the escapees were reeled in and trying to set up their punchy finishers.

However, no-one managed to control the run-in to the finish and the 90-degree bend 200 metres from home helped cause chaos that saw both Sagan and Boonen lose valuable yards as they were squeezed off the racing line and forced to slow down.

Demare timed his burst perfectly and took the bend at speed, acting as a slingshot into the final straight.

He had understood that the first man into the corner would be at a significant advantage and he charged down the inside line and emerged into the final straight with daylight between himself and the chasers.

Goss had the faster finish and ate into the gap but just ran out of tarmac before he could overhaul the Frenchman.

With the favourites and leaders all coming home safely in the bunch, Frank leads Roman Kreuziger by 23 seconds overall with last year's winner Rui Da Costa 35 seconds behind in third.