Boris Berezovsky and Russian human rights campaigners presented some new evidence of FSB involvement in the explosions that killed in excess of 300 people at a press conference in London on Tuesday.

Berezovsky also alleged that Vladimir Putin knew of the murderous campaign, and that the explosions were orchestrated to create the political climate for an attack against Chechnya leading to the eventual election of Putin as president. Until his appointment as prime minister two months earlier, Putin was head of the FSB.

The government blamed Chechen rebels for the attacks, although it never produced sufficient evidence to back up its claim.

Nikita Chegulain, a former undercover agent of the antiterrorist division of the FSB, said he possessed documentary evidence that proved that highly explosive hexogen was withdrawn from military bases and distributed secretely to regional organisations. He incriminates top government officials in the coverup; independent investigations have so far been blocked.

The panel brought attention to already known facts about a foiled explosion in Ryazan on 22 September 1999. The FSB was forced to admit that it had planted the device, when phonecalls amongst its agents were intercepted. Yet, simultaneously, head of the FSB Patrushev claimed that the explosives were actually sugar and that this was part of a so-called security exercise.

This sharply contradicts the version of the local police force which had determined that the substance was hexogen and that the detonator equipment was real and set for 5.30am – "the clock was ticking". Four explosives experts from Britain and France recently examined the available evidence from the Ryazan incident and concluded that the bomb was authentic.

Berezovsky came to money as a result of shady privatisation deals during the Yeltsin years. Being part of the "family" -the Yeltsin circle of insiders - he also accumulated extensive media interests. He helped mastermind the political rise of Putin through blatant media manipulation. However, he later fell out with the Putin administration and was forced to give up most of his media outlets. His remaining TV channel TV-6 was closed down by the courts in January in an extremely arbitrary fashion.

Berezovsky commissioned a documentary about the explosions by French filmmakers Charles Gazelle and Jean-Charles Deniau which was supposed to be shown on TV-6. A previous documentary "The Sugar of Ryazan" was shown on independent television station NTV. Observers suggest that this and critical coverage of the war in Chechnya may have prompted the Kremlin to clamp down on independent media including NTV, TV-6 and many others.

When asked about the "circumstantial nature of the evidence", Berezovsky replied that the facts presented were "stronger than the 11 September evidence" given by the US to justify its attack on Afghanistan. It remains to be seen whether independent investigations will ever be carried out in either Russia or the US.