More than 130 cyclists were arrested by police close to the Olympic Stadium on the opening night of the Games.
There were scuffles between police and cyclists on the outskirts of the Olympic Park at 22:30 BST on Friday.
People taking part in a monthly mass bike ride held in London said they were "kettled" near the stadium.
The police said cyclists ignored warnings and rode on Games Lanes ahead of the opening ceremony, but they did not respond to the kettling claim.
The Critical Mass ride is a pro-cycling event which takes place in London every month.
The Metropolitan Police said people were arrested under section 12 of the Public Order Act and for causing a public nuisance.
The force said two groups had been detained - the first on Bow Flyover and the other in Warton Road, Stratford.
The Met said up to 500 cyclists had gathered near Waterloo by 18:00 BST, five times the usual number that attended.
Police believed the demonstration "had the potential to cause serious disruption" and said officers used loud hailers and leaflets to explain the restrictions.
The Met said: "Officers were aware that a monthly cycle procession was due to take place yesterday, Friday 27 July, and made several attempts to engage with riders to discuss their plans.
"From the outset they attempted to cross the Thames, despite attempts by officers to prevent them.
"The procession split into smaller groups and some of them crossed to the north of the River.
"They travelled to the Stratford area, where there were large numbers of people and vehicles due to the Olympic Opening Ceremony.
"Cyclists continued to ride around the ORN [Olympic Route Network], despite numerous warnings and officers took action to detain the cyclists and over 130 people were arrested for breach of section 12 of the Public Order Act."
Kerry-Anne Mendoza, 31, who describes herself as a campaigner and writer, said: "We were cycling down the Bow Road [in Stratford] and the police directed us down a cul-de-sac.
"Then they kettled us in there."
She added: "They have not communicated with us or told us why we are being held here or when they will let us out."
Jonathan White, in his 50s, a former investigations officer in the Customs department, said he and other cyclists were kettled "for three hours" close to the stadium at about 21:00 BST before being arrested.
He said he was taken first to Charing Cross police station and then moved to Kilburn police station where he was bailed just after 06:00 BST on Saturday.
Mr White said his bail conditions, which apply until 19 September, prevent him from going within 100 yards of any Games venue or entering Newham with a cycle.
Joel Benjamin, who has been on several Critical Mass bike rides previously, said: "Usually there is a light police presence.
"[On Friday] there were far more police than I've seen before."
'Celebration of cycling'
He and Mr White said police used a sound system to tell cyclists there were restrictions placed on the ride but not what it meant.
Mr Benjamin, who was not arrested, said: "Basically, they didn't want us to go north of the river.
"I saw several cases of the police being aggressive and physical, dragging people off their bikes to the ground.
"I guess there were people there who are against the Olympics, but Critical Mass is really a celebration of cycling, there was no need to get so heavy handed."