Radical leftist leader Sergei Udaltsov was detained at the close of an opposition rally in downtown Moscow on Saturday, he told RIA Novosti by telephone from a police van.

Police grabbed him without explanations five minutes before the event’s end, scheduled at 10 p.m., said Udaltsov, who was detained more than 100 times at various protest events in recent years.

The activist called his supporters during the rally earlier in the day to stay and camp out at Prospekt Akademika Sakharova after the event’s end, but later urged them to disperse.

Police said Udaltsov ignored their demands to leave the venue and attempted to stage an unsanctioned march on a nearby boulevard, obstructing traffic.

Some 14,000 people showed up for the rally on Saturday, the latest in a string of anti-Kremlin protests ongoing in the Russian capital since December, city police said earlier. Organizers put attendance at 100,000.

No more arrests were reported at the event. Some 150 supporters of Udaltsov stuck with him until the rally’s end, but left the venue at his request and headed to the metro without confronting police.