Russia’s spy chief on Tuesday denied responsibility for the SolarWinds cyber attack but said he was “flattered” by the accusations from Washington and London that Russian foreign intelligence was behind such an advanced hack.

Britain and the United States have blamed Russia’s Foreign Intelligence Service (SVR), successor to the foreign spying operations of the KGB, for the hack which encompassed 9 American federal agencies and hundreds of private sector companies.

SVR Director Sergei Naryshkin, a close ally of Kremlin chief Vladimir Putin, told the BBC in Russian that “these claims are like a bad detective novel.”

Asked directly if the SVR was responsible for the SolarWinds attack, Naryshkin quipped with a smile that he would be “flattered” if the SVR had been responsible for such a sophisticated attack but that he could not “claim the creative achievements of others as his own.”

The SVR Director said he did not want to accuse Washington of being behind the attack but quoted from documents leaked by former National Security Agency contractor Edward Snowden to suggest that the tactics of the attack were similar to those used by British and U.S. intelligence agencies.

Washington and London cast Moscow as a dangerous former superpower which they say has poisoned enemies with radioactive isotopes and nerve agents, interfered in Western elections and conducted hacking operations across the world.

Naryshkin added that such accusations were absurd and that Moscow was not responsible for the cyber-attacks, hacks, poisonings, or interference in elections that it was blamed for.

The hack of SolarWinds, which was identified in December, gave access to thousands of government offices and companies that used its products. Microsoft President Brad Smith described the attack as “the largest and most sophisticated attack the world has ever seen.”

Britain’s GCHQ cyber spying agency said that it was highly likely that SVR was responsible for the SolarWinds attack.