The Russian prosecutor's office unexpectedly terminated a high-profile corruption probe today, saying charges would not be filed against magnate Boris Berezovsky in a case involving the diversion of cash from the national airline, Aeroflot, to a pair of Swiss companies.

The decision means that Berezovsky, one of Russia's most politically active tycoons who has close ties with some of President Boris Yeltsin's advisers and his daughter, will not face the possibility of prosecution, at least for now. The decision also underscores anew how infrequently the Russian authorities have been able to successfully prosecute influential businessmen and politicians on corruption charges.

Nikolai Volkov, the investigator, said he signed an order Thursday terminating the criminal probe of Berezovsky. He told the Interfax news agency that Berezovsky remains a "witness," and two former Aeroflot executives remain under investigation.

It was not clear why the case was abruptly closed down, but Volkov said the materials collected so far do not support preliminary charges brought in April. "We received part of the investigation materials from Switzerland, the analysis of which showed that the initial accusation that was brought against Berezovsky . . . did not find confirmation to a full degree," he said in a television interview tonight.

Volkov said the investigation has stopped "for this period of time," suggesting the probe might be restarted.

"Thorough expertise is needed to sort out" the materials obtained by the prosecutor's office, "which lay out new aspects of Berezovsky's financial activity," he told Interfax without elaborating.

Berezovsky is running for a seat in the lower house of parliament in the December elections and, if successful, would enjoy immunity from prosecution while in office.

Court papers released in Lausanne Oct. 16 alleged that Berezovsky and two executives of Aeroflot hid $600 million of hard currency in Switzerland. The figure was given to Swiss authorities by Russian investigators who asked for help. The Russian investigators said, according to the court papers, that Berezovsky and the two others, Aeroflot executives Nikolai Glushkov and Alexander Krasneker, took $400 million in Aeroflot profits and $200 million in air traffic fees and hid the money in two Swiss companies, Andava and Foros Services.

The two firms were raided by Swiss authorities in July and their bank accounts frozen. The firms denied wrongdoing.

Berezovsky, 54, one of the most outspoken of Russia's wealthy oligarchs, returned to Russia last spring to face preliminary charges in the Aeroflot case. Today Volkov personally gave him a copy of the order shutting down the investigation.

"Right from the moment the criminal proceedings were launched," he said, "I had been saying that I had committed no illegal act and that the criminal proceedings against me, just as those against Nikolai Glushkov and Alexander Krasneker, had been prompted by purely political motives."

"I am satisfied that the investigator Volkov showed objectivity . . . at this stage and drew what was the only correct conclusion . . . that I had not broken any law."

Berezovsky has been locked in a bitter election feud with Moscow Mayor Yuri Luzhkov and former prime minister Yevgeny Primakov, who are running at the head of a parliamentary ticket. Both also have presidential ambitions.

Berezovsky's newspapers and television stations have been running smear campaigns against both men, while Luzhkov's media arsenal has been unleashed against Berezovsky.

Today, Luzhkov again took aim at the tycoon, telling journalists that Yeltsin "is no longer in control of events" and that Berezovsky is the hidden force in the Kremlin. He said Berezovsky has been the "chief organizer" of the "harassment" of Luzhkov. Speaking of the highest levels of power in the Kremlin, Luzhkov said, "Everything is absolutely rotten up there."