The final stage of the Vuelta a Espana was abandoned after pro-Palestinian protesters entered part of the course in the centre of Madrid.
Protesters knocked down barriers and occupied the road at several points on the course including Gran Via, where cyclists were due to pass multiple times.
More than 1,000 police officers had been deployed on to the streets of the Spanish capital, with demonstrations expected.
Danish cyclist Jonas Vingegaard, who led going into the 21st and final stage, was declared the winner - a first Vuelta title for the two-time Tour de France champion.
Tradition dictates rivals do not seek to overhaul the leader on the last day of a Grand Tour.
Britain's Tom Pidcock - of Q36.5 Pro Cycling - finished third, behind UAE Team Emirates-XRG's Joao Almeida.
The riders were stopped with around 60km remaining as they arrived at the finishing circuit in Madrid before the stage was abandoned.
There have been various protests against the Israel-Premier Tech team throughout this year's Vuelta, forcing some stages to be shortened.
Riders have crashed as a result of the protests, with some saying they have been worried for their safety.
Last week, Israel-Premier Tech began racing in modified jerseys which did not display their team name.
There was no podium presentation for Vingegaard or the winners of the other race jerseys.
It's a pity that such a moment of eternity was taken from us, said Vingegaard.
I was looking forward to celebrating this overall win with my team and the fans. Everyone has the right to protest, but not in a way that influences or endangers our race.
Clashes continued after the race was abandoned, with protesters throwing bottles of water and other objects at police.
Race organisers had already shortened the 21st and final stage of the Vuelta from 111.6km to 103.6km, but ultimately decided to abandon it altogether due to safety concerns for both riders and spectators.
Cycling journalist Brian Smith pointed out that the protests were anticipated after earlier disruptions during the race.
The current protests are linked to escalating tensions surrounding the Israeli-Palestinian conflict, with recent military actions intensifying demonstrations in various countries, including Spain.
Spanish Prime Minister Pedro Sanchez expressed admiration for the protests while Madrid's mayor blamed Sanchez's comments for provocation that led to the race's abandonment.
Israel’s foreign minister condemned the Spanish government's handling of the situation, emphasizing the international ramifications of such protests on sporting events.