By Katya Golubkova and Polina Devitt
MOSCOW/PARIS (Reuters) - The Kremlin said on Wednesday it will spare no effort to defend the rights of Suleiman Kerimov, a Russian businessman and lawmaker who was arrested in the French Riviera resort of Nice in connection with a French tax evasion case.
Shares in Polyus, Russia's biggest gold producer which is controlled by Kerimov's family, were down on the news of his detention.
The 51-year-old billionaire would be presented to a judge with a view to formally placing him under judicial investigation, a French public prosecutor said in Nice on Wednesday.
Under France's legal system, being formally placed under investigation often, but not always, leads to a person being sent to trial.
"We will do everything in our power to protect his lawful interests," Kremlin spokesman Dmitry Peskov told a conference call with reporters. "Intensive work is now being undertaken by the foreign ministry."
A representative for Kerimov in the upper house of parliament, where he sits as a lawmaker, declined to comment on the case on Wednesday when contacted by Reuters. Polyus declined to comment.
Russia's state-run Rossiya 24 TV station, citing an unnamed source, reported that Kerimov had denied any guilt.
In the lower house of parliament, lawmaker Rizvan Kurbanov asked the Russian foreign ministry to make representations on Kerimov's behalf with the French authorities.
"We have still not received from the French authorities any explanation of the reasons for the detention of our colleague," Kurbanov told parliament.
"All this testifies to an unprecedented demarche by the French," he said, adding that he hoped the Russian foreign ministry would issue a formal protest.
Shares in Polyus were down by more than 3 percent in early trade in Moscow but since then recovered some ground to trade at minus 2.3 percent by 1342 GMT.
Originally from the mainly Muslim Russian region of Dagestan, Kerimov built his multi-billion natural resources business through a combination of debt, an appetite for risk, and political connections.
He owned top flight soccer club Anzhi Makhachkala until he sold it in 2016.
Kerimov's fortune peaked at $17.5 billion in 2008 before slumping to just $3 billion in 2009, according to Forbes magazine, due to so-called margin-calls on his assets triggered by the 2008 global financial crisis.
In March this year, Russian President Vladimir Putin signed a decree giving Kerimov the state award "For Services to the Fatherland, second class" for his contribution to Russian parliamentary life.
French police arrested Kerimov at Nice airport on Monday evening.
A French judicial source said the investigation centered on the purchase of several luxury residences on the French Riviera via shell companies, something that would have enabled Kerimov to reduce taxes owed to the French state.
(Additional reporting by Elena Fabrichnaya, Dmitry Solovyov and Olga Sichkar in MOSCOW and Mathias Galante in PARIS; writing by Katya Golubkova; Editing by Christian Lowe and Richard Balmforth)