The head of Societe Generale's Russian unit Rosbank faced up to seven years in jail for bribery on Thursday after Russian investigators released a film of him with cash piled on his desk in what several bankers said may have been a set-up.

The case could increase alarm among international investors and sheds a damaging light on business practices in Russia, where SocGen is one of the few Western banks left in a market dominated by homegrown state players.

Investigators said on Thursday they had opened an official criminal investigation against Vladimir Golubkov, who was detained on Wednesday, and his senior vice president, Tamara Polyanitsyna - a final step before formally charging them.

Yet more than 24 hours after his arrest, Golubkov had still not been brought before a court. "It's not clear when he will be charged; they are still conducting inquiries," his lawyer Dmitry Kharitonov told Reuters.

Kharitonov complained that Golubkov, 47, had been held in "disgraceful conditions, forced to remain seated throughout, and was not feeling well.

Golubkov worked through the ranks at Rosbank to take the helm in 2008. One of the bank's former owners, billionaire politician Mikhail Prokhorov, expressed outrage at the investigation, saying he had petitioned the court where Golubkov was expected to be charged for him to be freed on bail.

"I know him very well," said Prokhorov, who ran on a liberal ticket against Vladimir Putin in last year's presidential election. "He was always an honorable, professional man, and I'm certain he won't hide anywhere."

Other leaders of Russia's financial community also spoke out in support of Golubkov, and said he might have been entrapped.

"The accusations simply don't fit - although the law enforcement authorities are entitled to their version and to investigate," Garegin Tosunyan, president of the Association of Russian Banks, told Reuters.

"If you ask me, it is unlikely that he would stoop to such commercial bribery. I hope that investigators will consider the possibility that he was deliberately set up."

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The Interior Ministry used the increasingly common practice in high-profile cases of releasing video footage of a police raid. It showed officers with automatic weapons barging past security guards into Rosbank's headquarters in central Moscow.

The film then cut to a scene that showed Golubkov standing behind his desk, which had several wads of 5,000 rouble ($150) notes on it. The cash was said by investigators to total 5 million roubles ($160,000). Golubkov, wearing a light grey suit, looked into the camera but did not speak in the footage.

"Golubkov demanded, via his subordinate Polyanitsyna, more than $1 million from a businessman to extend the maturity and reduce the interest rate on a multi-million-dollar loan," the Investigative Committee said.

Lawyer Kharitonov said Golubkov had denied committing the crime. It was not clear who was representing Polyanitsyna. Officials at Rosbank declined to comment on her behalf.

Rosbank moved swiftly to try to limit damage from the case, saying it was cooperating with the investigation and that First Deputy CEO Igor Antonov would replace Golubkov on an interim basis. Operations and client service continue uninterrupted.

"We are disturbed and upset about what has happened," Antonov told the state-owned Rossiya 24 news channel.

He described the arrest of Golubkov as a "raid" reminiscent of the chaotic years following the collapse of the Soviet Union. "It reminds me of the good old 1990s. We haven't seen anything like it for ages," he said.

The charges are likely to lead to soul-searching at SocGen headquarters in Paris, which has reaffirmed its commitment to Russia, a market it first entered at a high price in 2006 but where it has struggled to turn a profit.

Golubkov was in charge of a turnaround strategy at Rosbank, into which SocGen's other Russian banking interests were folded in 2011. But, plagued by high costs and declining market share, Russia's ninth-largest bank lost money last year.

SocGen declined to comment.

"From SocGen's point of view, this is an affair that concerns only individuals, not Rosbank or its risk controls," a banking source said.

Western and Russian bankers say loan 'facilitation' payments are common in Russian banking, but they rarely come to light unless someone seeking to settle a score turns to the law enforcement authorities.

According to media reports on Thursday, an executive at a car dealership informed on Golubkov after paying several installments of a bribe to restructure an $80 million loan.

The Kommersant financial daily, which often has detailed accounts of law-enforcement operations, said Polyanitsyna had been arrested the day before and agreed to cooperate with investigators in handing over the final tranche of the bribe.

A former Rosbank executive, who recently left the bank, told Reuters it could help the French bank in the long run, by helping to resolve longstanding disagreements between Paris and the local staff.

"This is such a scandal - though I must say it might help reinforce SocGen within this big Russian organization if Golubkov steps down," said the executive, who declined to be named.

($1 = 31.3252 Russian roubles)

(Additional reporting by Lionel Laurent in Paris; editing by Elizabeth Piper and Will Waterman)