In an extraordinary public appearance, Federal Security Bureau (FSB) officers said the agency was being used "to settle accounts with undesirable persons, to carry out private political and criminal orders for a fee, and sometimes simply as an instrument to earn money".
The men, several wearing reflective sunglasses and one clad in a black balaclava, unveiled their allegations at a press conference in Moscow, plunging the agency into one of its more serious, and mysterious, post-Soviet scandals.
"Our aim is to draw public attention to the deviations in the work of the Federal Security Bureau that are exceedingly dangerous for society and which have become features of its activities," they said in a statement.
"We do not want the shadow of the criminal actions of a number of officials to be cast on the service and its honest officers." The statement was signed by two colonels, two majors and a senior lieutenant.
Security officers publicly attacking their bosses is unheard-of in post-Soviet Russia, and immediately dominated television news headlines, casting a shadow over the meeting in Moscow between President Boris Yeltsin and the German Chancellor, Gerhard Schroder.
In recent years, reports have regularly linked organised crime and the FSB, which has suffered from low morale, poor pay and a brain drain, following the break-up of the far larger KGB. Thousands of ex-KGB agents have taken paid jobs in the shady world of Russian business and banking.
Some media reports have linked FSB elements with contract killings, bombings and hostage-taking. But this is the first time that officers, apparently from the heart of the security system, have so openly spelt out allegations of top level corruption.
They acknowledged that they risked reprisals. "We were told, 'we will first boot you out of the service and then stifle you like pups'," said Lt-Col Alexander Litvinenko.
The most dramatic revelation has been the men's claim that a senior FSB officer ordered the colonel to kill Boris Berezovsky, one of Russia's top business and media magnates, who played a leading role in releasing two British hostages in September. Lt-Col Litvinenko, Mr Berezovsky's former bodyguard, claimed he did not carry out the order, which he received last December, because he regarded it as illegal.
The colonel said as a result he was assaulted, received death threats and was threatened with prosecution. In May, media reports accused him and his colleagues of being involved in murders, assaults, torture and extortion.
Lt-Col Litvinenko claimed one FSB officer also accused him of "preventing patriots from the motherland from killing a Jew who robbed half his country". Mr Berezovsky has Jewish roots, an issue that has acquired significance because of the resurgence of anti-Semitism in Russia.
Another officer, Major Andrei Ponkin, yesterday claimed that in late 1977 the FSB leadership planned to kidnap the brother of a prominent Moscow businessman, Umar Dzhebrailov, Hussein, then take him to a country house. "In case of resistance ... we were ordered to kill the policemen who guarded him and then kill him, as one of the options," he said. The order was never carried out.
The agents argue that these were not isolated incidents. "The order to assassinate ... Berezovsky, unfortunately, is not an exceptional event in the present life of the FSB," said their statement.
The director of the Federal Security Bureau, Vladimir Putin, has confirmed that Russia's chief military prosecutor's office is investigating the Berezovsky case. But he has also threatened to sue accusers if their claims prove groundless.
The officers have stressed the director is not their target and the agency's problems began under his predecessor, General Nikolai Kovalyov.