Nails thrown on route of Wiggle Etape Cymru bicycle event
Saboteurs targeted a bicycle event featuring 2,000 riders by throwing tacks and nails on the route in three separate places.
Dozens of those taking part in the 88-mile (142km) Wiggle Etape Cymru ride through Wrexham and Denbighshire on Sunday suffered punctures.
Organisers of the event said the action was a danger to riders on the day and a menace for drivers for weeks to come.
Wrexham council said the event was "hugely successful" despite this.
The event, in its third year, began and ended at Bangor-on-Dee racecourse, Wrexham, after taking in the Horseshoe Pass in a challenging route involving thousands of metres of climbing.
The ride closes some roads for up to eight hours which organisers suspect may be the reason behind the incident.
Nick Rusling, of event organisers Human Race, said he understood the temporary closures were "an inconvenience to some" but hoped people would find the "positives outweigh the negatives".
He said: "It's understandable that this event is not for everyone and it can be disruptive but this event does much for the local economy.
"It's a unique experience for the riders. People come from miles to do it and spend money in the region. It would be foolish to try and sabotage it."
He said the organisers worked with agencies and local people to ensure those who had to make trips along the route on the day such as carers, the elderly and farmers had a motorcycle marshal to accompany them.
He added: "We do understand that it can be prohibitive but it's one day a year with plenty of notice.
"The police were on hand to remove the bulk of the tacks but a lot will stay on the road and affect local people for weeks to come. It's not just the cyclists."
Mr Rusling said a motorbike safety marshal was put out of action after getting a puncture.
Wrexham council said it was looking forward to the event's return next year.
It said: "It is obviously disappointing that a small minority attempted to spoil what was a fantastic event.
"We hope that North Wales Police find those who were responsible.
"But this should not detract from what was a hugely successful event that attracted 2,000 cyclists from all over the country."
Clwyd South MP Susan Elan Jones called for those responsible for throwing the nails and tacks to be prosecuted.
She said: "Most people in our area will want to see the thugs behind these appalling acts dealt with properly. We need to have zero tolerance for this sort of yobbish behaviour."