MOSCOW (Reuters) - Moscow police interrupted a play featuring the trial of punk rockers Pussy Riot on Sunday and warned its Swiss director for violating visa rules, in what a government critic said was part of an anti-Western campaign.

Federal Migration Service officers delayed the performance of "Moscow Trials" at a theatre at Moscow's Sakharov center for an hour as they issued a verbal warning to director Milo Rau, according to news agency Interfax and website Publicpost.ru .

The play features three recent trials in Russia, including one which ended in August with jail terms for ""hooliganism motivated by religious hatred" for three members of the Pussy Riot band for staging a profanity-laced protest in Moscow's main cathedral last February.

The band members, one of whom was later released on appeal, said the protest was meant to draw attention to close ties between the Russian Orthodox Church and the Kremlin.

Kremlin critic Boris Nemtsov, a deputy prime minister from 1997 to 1998, said the raid on the theatre was part of an anti-Western drive fostered by President Vladimir Putin.

"Our leadership is suffering a grave form of spymania ... and the fight against the West has become a number one priority in its domestic and foreign policies," he said.

Russia's relations with the West have cooled since Putin returned to the presidency last May.

On January 1, Russia banned adoptions of children by U.S. parents in response to U.S. legislation imposing visa and asset restrictions on Russians accused of violating human rights. Russia has also forced non-governmental organizations receiving overseas funding to register themselves as "foreign agents".

The migration officials raiding "Moscow Trials" were accompanied by Cossacks, a traditionalist group whose recent revival has been encouraged by Putin, according to Publicpost.ru and twitter reports from the scene.

No formal punishment was imposed on Rau for allegedly violating visa conditions, Interfax quoted Sergei Kalyuzhny, the Federal Migration Service's deputy head as saying.

"He entered (Russia) on a business visa, which does not allow any working activity," Kaluzhny said.

Putin's return to the presidency last year was soured by the biggest political protest over the past decade, which analysts say led the Kremlin to ramp up nationalist rhetoric.

(Reporting by Alexei Anishchuk; Editing by Jason Webb)