The agency has regularly faced criticism for undertaking politically motivated inquiries, especially those involving opposition politicians. It has also prosecuted scientists and academics for what it has contended were illegal transfers of classified information abroad.

And now, the Kremlin seems bent on making the F.S.B. even stronger. Parliament, controlled by Mr. Putin’s party, is in the process of approving legislation that would allow F.S.B. agents to warn people that their activities were “unacceptable” and leading toward a crime. The K.G.B. once employed a similar practice against Soviet dissidents.

The F.S.B. would not comment on Ms. Kazakova. Regional prosecutors said her arrest had nothing to do with the security agency’s resort. But they could not explain why in many other municipal corruption cases in the region, the F.S.B. was not involved, and defendants were treated far more leniently.

“There are laws in Russia, but the security services are beyond any laws,” said one of Ms. Kazakova’s lawyers, Dmitri Dmitriyev. “They act with total impunity. They can undertake special inquiries, collect information on people, violate fundamental human rights, put people in prison, keep them there as long as they want, manipulate judges and manipulate prosecutors. This case is just a demonstration of all this.”

Ms. Kazakova’s longtime companion, Dmitri Matveyev, 40, who had lived with her for years, wanted to marry her after her arrest, but the judge in the case would not allow it. After Mr. Matveyev gave an interview to The Times, he said he was visited by two F.S.B. agents, who instructed him not to speak to The Times again.

“I told them that I am not going to listen to them,” Mr. Matveyev said. “It has been two and a half years, and that has been a long enough period of silence. That is why I am going to talk.”

Getting Things Done

Ms. Kazakova made her fortune operating hotels and markets in Irkutsk, earning praise for her savvy all the way to the Kremlin. She then turned her attention to Listvyanka, a downtrodden fishing village on Lake Baikal, an environmental masterpiece that by some estimates has 20 percent of the world’s fresh water.