London Metropolitan Police are cracking down on a Critical Mass bicycle protest ride in London near the Olympic Games opening ceremony. Critical Mass rides take place in cities around the world on the last Friday of every month, but London police had put special conditions on this Friday’s ride due to the Olympics.

Just hours ago, Metropolitan Police had used Twitter to reiterate the conditions of the ride, even using the #CriticalMass and #protest hashtags.

Much the like Occupy movement, Critical Mass is considered “decentralized,” with no specific platform or manifesto. So, what is this protest about, exactly?

Cyclists are being “kettled,” or corralled, by police officers. Some tweeters claim police are using pepper spray as well.

A group called Our Olympics vowed in its Twitter profile to make “the Olympics of London 2012 the greatest act of nonviolent civil disobedience of our age.”

Supporters of the protest, including Occupy London and the Black Bloc, were quick to declare London a police state.

There’s little sympathy from some quarters.