There were scuffles between police and cyclists on the outskirts of the Olympic Park.
People taking part in a monthly mass bike ride held in London said they were “kettled” near the stadium.
The Metropolitan Police said they had made arrests for Public Order offences but have not responded to the kettling claim.
Dozens of cyclists were blocked by police vans from proceeding, Scotland Yard said.
Two groups of protesters were arrested on suspicion of breaching protest conditions and causing a public nuisance, Scotland Yard said.
The cyclists were identified as members of an activist cycling club that meets monthly for mass bike rides.
A police order had prohibited the protesters from traveling into the Olympic Park area in east London during Friday night's opening ceremony, but members had tried to pedal their way through the security cordon.
Police said some of those arrested were in police stations while some have been bailed, but no details were given.