Police in Moscow have broken up a rally by Russian opposition activists, and detained at least a dozen of them.

Authorities started rounding up the protestors Monday, after a rally organizer told the demonstrators they each could carry a sign and act as a one-man picket, which did not need official permission. The protesters say they were illegally taken into custody after police began dragging them into vans.

The activists held the unauthorized rally outside the Russian Election Commission building to demand free and fair parliamentary elections in December and protest what they called “illegal” or “fraudulent” elections.

They say President Dmitry Medvedev and Prime Minister Vladimir Putin are “hijacking the vote” after Mr. Medvedev agreed not to run for president so Mr. Putin can retake the office he gave up in 2008 due to term limits.

The opposition says the elections are “fake” because a number of opposition parties have been denied registration and will not be able to take part in the elections.