MOSCOW (Reuters) - When does a legitimate Russian political protest become an illegal gathering? Answer: When a second person joins in to spoil it.

Russian satirist Viktor Shenderovich speaks in a court building after he was detained protesting in support of opposition leader Garry Kasparov in Moscow November 29, 2007. Shenderovich, a radio journalist and political satirist, was holding a sign saying Free Garry Kasparov outside police headquarters on Wednesday and was detained after a provocateur came out with a flag and stood beside him, he told Reuters. REUTERS/Grigory Dukor

So says Viktor Shenderovich, a radio journalist and political satirist who had been staging a lone protest outside a Moscow police headquarters Wednesday, holding a sign saying “Free Garry Kasparov.”

“Then a provocateur came out with a flag and stood beside me,” Shenderovich told Reuters.

Shenderovich said police waiting in a nearby vehicle then walked over to detain him and the unknown accomplice.

“The legally-allowed lone protest had turned into an unsanctioned demonstration,” he told Reuters.

Kasparov, a former chess champion and leader of a minor opposition political party, was arrested by Moscow police last weekend after a sanctioned protest march he led was broken up by riot police. He is set to be released from jail Thursday.

“A lone protest doesn’t need official permission,” said Shenderovich at the Mirovoy Court in Moscow.

Russian authorities closely monitor demonstrations, authorizing the number of attendees, where and when they can rally.

Shenderovich was one of several lone protesters detained on Wednesday outside the police headquarters and charged.

“The provocateur told the police, joyfully, when asked what he was doing out there, ‘Provoking. It’s what we have to do’,” said Shenderovich.

“It speaks to the degradation of our society because it’s all being done in the open,” he said.

“The police know it is provocation...their proof is just a couple of empty nothings.”

The Moscow police press service referred all questions about Shenderovich to a separate spokesman who could not be reached for comment. Thursday the Russian Ministry of Emergency Services said it would assign more than 50,000 firefighters and rescue workers to join the expected 450,000 police called up to patrol more than 96 thousand polling places Sunday during elections.