Russian law enforcement agencies on September 5 raided premises of the Renova Group of billionaire Viktor Vekselberg and its subsidiary T Plus in connection with a bribery probe involving former state officials.

As masked operatives swooped on offices in Moscow and Russia's north-west Komi republic, there was a knock-on effect on the VimpelCom mobile operator, whose head of Russia operations is also implicated in the probe through his earlier work with a Vekselberg-owned company.Mikhail Slobodin concurrently resigned as head of VimpelCom's Russia operations.

Vladimir Markin, the spokesman of Russia’s powerful Investigative Committee, said authorities in Komi opened a criminal case against former and acting managers of  Kompleksnye Energeticheskiye Sistemy (KES) company, of which T Plus is the legal successor, on suspicion of large-scale bribery, media reports said.

Investigators claim that from 2007 to 2014 the suspects bribed officials currently involved in a criminal case against the republic’s ex-head Vyacheslav Gaizer with money and other assets. “The total amount of funds transferred as money reward made over RUB800mn ($1,232,000),” Markin said.

The spokesman also confirmed that searches and interrogations of witnesses were being carried out at the Moscow offices of T Plus and related companies with support from the regional and central directorates of Russia's Federal Security Service (FSB).

A Renova representative said two executives in companies controlled by Vekselberg were being questioned by law enforcement, Reuters reported. "The company will cooperate with law-enforcement bodies. All staff are working as usual," Renova spokesman Andrey Shtorkh told the newds agency. "This is not connected with Vekselberg personally."

Vekselberg, who Forbes magazine ranks as Russia's seventh richest man, was not immediately available for comment, Reuters said. The 59-year-old bsuinessman is one of a shrinking group of tycoons who amassed their fortunes independently of the Kremlin and saw their influence diminish as President Vladimir Putin consolidates the inner circle of businessmen around him.

Slobodin, the former head of KES, resigned from his current position as head of the Russian division of New-York-listed mobile operator VimpelCom, as the investigation was announced. Slobodin's whereabouts are unknown, with TASS quoting unnamed security sources as saying that he might be in London. Slobodin resigned from VimpelCom because he did not want to compromise his employer, a source close to the company told the Vedomosti business daily.

It is not clear whether VimpelCom's operations will also be part of the bribery investigation. In 2016 the company had to set aside $795mn for violating Dutch anti-corruption laws and the US Foreign Practices Act for allegations of corruption and money laundering charges related to its operations in Uzbekistan.

VimpelCom's main shareholder (47.9%) is LetterOne, an investment vehicle of Russian billionaire's Mikhail Fridman's Alfa Group. Together with Vekselberg's Renova, Alfa formed AAR consortsium, which held a 50% stake in Russia's third largest oil producer TNK-BP until bought out in 2013 by Kremlin-controlled oil giant Rosneft.

Before joining VimpelCom, Slobodin was TNK-BP's Executive Vice President for Strategy and New Business Development.