Police reportedly kettled dozens of protesters close to the Olympic Park on Friday night.

The protesters were from the group Critical Mass, a cycling activist organisation.

Police said they had been given permission to hold a demonstration in south London, on the condition that they did not the River Thames.

The Metropolitan Police Press Bureau said the protesters violated that condition and a number were arrested at Tower Bridge, to the east of central London.

Several hours later, around 40 police vans were seen on Stratford High Street, a short distance away from the Olympic Park stadium.

The incident occurred just as the Olympics Opening Ceremony was getting underway.