The deputy head of the Russian Jewish Congress Mikhail Mirilashvili has been arrested by police in St Petersburg and charged with kidnapping.
The chairman of the Jewish Congress, Vladimir Gusinsky, is currently under house arrest in Spain, awaiting possible extradition to Russia.
The Jewish community in Russia will be concerned to see its two top men in confrontation with the authorities, though Russian police say the two cases are not related.
The latest arrest comes as the Israeli President, Moshe Katsav, is on an official visit to Russia.
Mr Mirilashvili was due to travel with the Israeli President's delegation when they go on from Russia to Georgia on Thursday.
Business connections
Mr Mirilashvili has a business connection with Mr Gusinsky, too. He is a director of a St Petersburg-based company, Russkoye Video.
Mr Gusinsky's Media-Most group bought Russkoye Video in 1997 - a purchase which prompted an investigation by the Prosecutor-General's office.
It was claimed that the $10m dollars which Mr Gusinsky paid was an undervaluation, and last June he was accused of cheating the state.
The charges were dropped, but then brought up again when the head of Media-Most failed to appear for questioning by prosecutors in November.
The Russian authorities insist that the arrest of Mr Mirilashvili is not connected to Mr Gusinsky.
But the links between the two men are bound to raise doubts about this, especially as it comes at a sensitive time both in the Gusinsky affair, and for Russo-Israeli relations.