Italy's Filippo Ganna won a shortened individual time trial on stage 18 of the Vuelta a Espana as Britain's Tom Pidcock retained his third place in the overall standings.

UAE Team Emirates-XRG's Joao Almeida, who is second in the general classification, took 10 seconds off the advantage of overall race leader Jonas Vingegaard.

The stage was reduced from 27.2km to 12.2km to ensure "greater protection" for riders because of security concerns resulting from a series of pro-Palestinian protests during the three-week race.

Police numbers were also ramped up, with hundreds of protestors waving flags along the route and whistling riders from Israel-Premier Tech.

And French news agency AFP reported that two protestors were detained for trying to jump over barriers.

Two-time world time trial champion Ganna, 29, lived up to his billing as the favourite, with the Ineos Grenadiers rider edging out Australian Jay Vine by a second in Valladolid.

"Obviously, with the news of the change in the parcours [route] last night it was a bit strange, but I tried to do the best today," said Ganna, who was 10 seconds quicker than anyone else over the final four kilometres.

"The first part I didn't find the correct rhythm and in the final I tried to push over without thinking of the numbers. I am really happy for today."

While Ganna's fast finish ensured he pipped Vine, all eyes were focused on the battle at the top of the general classification.

Almeida finished strongly to put time into Visma-Lease A Bike's Vingegaard and the Portuguese rider now sits 40 seconds behind the Dane with two competitive stages of racing remaining.

Q36.5 Pro Cycling's Pidcock finished 29 seconds behind Ganna but managed to extend his advantage over Australian Jai Hindley in the battle for the final podium spot by three seconds.

With a relatively flat 161.9km run from Rueda to Guijuelo scheduled for Friday, it raises the prospect of a huge day in the mountains on Saturday's penultimate stage with a summit finish on the Bola del Mundo.