Boris Kuznetsov, a prominent lawyer who challenged the security services' wiretapping of his client, has applied for political asylum in the United States, his Moscow attorney said Tuesday.

Kuznetsov fled Russia in July after authorities accused him of divulging state secrets by providing evidence of the wiretapping to the Constitutional Court.

Kuznetsov has taken part in an array of high-profile cases, including representing the family of murdered journalist Anna Politikovskaya, a fierce Kremlin critic, and representing families of sailors who died in the Kursk nuclear submarine disaster in 2000.

By seeking asylum, Kuznetsov is "striving to secure himself from lasting and steadfast criminal prosecution," his lawyer Robert Zinoviev told The Associated Press.

Kuznetsov is one of many Russian lawyers to face official pressure after or while working on sensitive high-profile cases or on behalf of clients whom the government perceives as opponents. The government has been solidifying its control over the justice system.

Kuznetsov had appealed to the court to rule on whether the Federal Security Service, the successor of the KGB, had violated the rights of his client, a former member of the upper house of parliament, by tapping his phone conversations without a court's authorization.

His client, Levon Chakhmakhchyan, was arrested in February on suspicion of accepting a $300,000 bribe. Security service agents claim to have caught him in a sting operation.