Frenkel has protested his innocence and his lawyer, Igor Trunov, said he would appeal.
"We think the court decision is groundless, and we will appeal within three days at Moscow's City Court," Trunov said. "There is no reason for the case as no real evidence was presented to court. We have heard only baseless charges that he [Frenkel] plans to disappear, and that he plans to continue his criminal activities. So this is why we plan to appeal the [court] decision."
Frenkel was the director of a private bank that Kozlov shut down three months before he was shot dead as he left a soccer game in Moscow last September.
The same court on January 12 approved the arrest of another suspect, Liana Askerova.
Kozlov actively campaigned against corrution and money laundering in Russia's banking system.
Citizens of Russia's Urals region protest against alleged corruption in connection with a proposed smelting plant on Lake Shartash (TASS)
'A NATIONAL THREAT': Russian President Vladimir Putin highlighted the crippling problem of corruption during his annual address to the Federal Assembly in May. He emphasized the damaging impact of corruption on the country's economy and pledged to rid Russia once and for all of a "serious obstacle" ...(more)