MOSCOW—Russian law enforcement agencies opened a criminal case against Lyubov Sobol, an ally of Kremlin critic Alexei Navalny, and took her in for questioning early on Friday after raiding her home, Navalny and his supporters said. There was no immediate comment from the police. Supporters of Navalny said the police action appeared to be a response to Sobol visiting the home of an alleged FSB security service agent in Moscow. Navalny had earlier said the man took part in a botched plot to poison him in August. The FSB has dismissed Navalny’s allegations as a provocation designed to discredit it. Sobol was briefly detained on Monday after visiting the alleged agent’s flat and ringing the doorbell. She was not let into the man’s flat. But Ivan Zhdanov, a lawyer for Navalny’s anti-corruption organization, said police suspected Sobol of violating the sanctity of someone’s home with the use or threat of …