Cyclists taking part in an event in the New Forest were targeted by saboteurs who placed tacks on the road to puncture tyres, police said.
Officers conducted house-to-house inquiries in the village of Bransgore after 15 cyclists taking part in the Wiggle New Forest Spring Sportive suffered punctures on Saturday, Hampshire Police said.
It is the second time the 84-mile race in the picturesque national park has been targeted, and it came after posters were put up locally last week warning of the "abuse of our tranquil locality" caused by the 2,000 cyclists taking part.
Martin Barden, of race organiser UK Cycling Events, said: "It was surprising and disappointing to see a handful of anti-cycling campaigners trying to disrupt the event again this year by throwing tacks on to the road on several occasions.
"Our support teams, however, cleared these away before they could harm the riders, local drivers and New Forest animals."
He added that the majority of local people were supportive of what had been overall a successful event, cheering and clapping the riders.
A Hampshire Police spokesman said they were alerted to reports of tacks in Braggers Lane in Bransgore, on the south-western edge of the New Forest.
He said: "Fifteen cyclists suffered punctures, nobody was injured. Police removed the tacks and house-to-house inquiries were undertaken to identify if any witnesses had seen what had happened."