Opposition leader Sergei Udaltsov, center back, speaks at an unsanctioned rally at Pushkin Square in Moscow, Russia on Saturday. Russian police detained two dozen protesters in Moscow as hundreds rallied in downtown Moscow to protest Kremlin's policies. (Ivan Sekretarev/AP)

Police on Saturday detained 23 protesters, including Russia’s best-known environmental activist, on charges of holding an unsanctioned rally. They had been demonstrating in Revolution Square in the heart of the capital in support of two men arrested Tuesday in southern Russia in a dispute over construction in a forest of rare pines.

The protest was what Russians call a “single-digit” demonstration. Under the law, individuals can stand alone and hold signs without getting a permit first. Protesters have adopted a technique of spelling each other while keeping a sign in the air — but on Saturday, after letting the rally proceed, police took most of those attending into custody anyway, including Yevgenia Chirikova, who has made a name for herself trying to defend the Khimki Forest outside Moscow against a proposed highway.

They face fines and administrative charges, one of the protesters told the Interfax news agency during a cellphone call.

The rally was in support of Suren Gazaryan, a 37-year-old zoologist, and his attorney, Viktor Dutlov, who were arrested Tuesday night and sentenced to 10 days in jail. Gazaryan has been protesting plans by the governor of Krasnodar region to build a country house and compound in a nature reserve, and was already facing a five-year sentence on a hooliganism charge.

At one point, a police officer grabbed the sign that was being held up and stuffed it in a police van, while the small crowd jeered and a flying wedge of Interior Ministry troops blocked it. A man instantly unfurled another sign. “A nature reserve is no place for palaces,” it read.

Another rally, in support of a businessman convicted of fraud and the members of a feminist punk band who were arrested after singing a song against President-elect Vladimir Putin in Moscow’s main cathedral, went off without incident in Pushkin Square. Among the speakers was Sergei Udaltsov, leader of the Left Front, whose 10-day jail sentence for trying to lead an unsanctioned march last weekend was overturned on Friday.