Britain was on Monday embroiled in a growing diplomatic row with Russia and Turkey following revelations that their leaders were “spied on and bugged” by British and American intelligence agencies during the 2009 London summit of G20 countries.

The disclosure is likely to cause tensions at the summit of G8 leaders which got under way in N. Ireland with Russian President Vladimir Putin expected to demand an explanation from his host, the British Premier David Cameron, and the U.S. President Barack Obama, who is also attending the conference.

Russian officials were reported as saying the surveillance claims would strain the already tense U.S.-Russian relations, while in Ankara the Turkish Foreign Ministry summoned the British Ambassador for a dressing down.

Earlier, The Guardian revealed that world leaders who attended G20 conferences in London in April and September 2009 had their top secret communications intercepted “on the instructions of their British government hosts” with delegates being “tricked” into using internet cafes set up by GCHQ, U.K.’s intelligence hub.

Among those specifically targeted were the then Russian President Dmitry Medvedev, the Turkish Finance Minister Mehmet Simsek and delegates from South Africa with the aim of getting an advantage in negotiations over dealing with the international financial crisis.

The Guardian claims were based on documents leaked by the U.S. whistleblower Edward Snowden.

“The documents suggest that the operation was sanctioned in principle at a senior level in the government of the then Prime Minister, Gordon Brown , and that intelligence, including briefings for visiting delegates, was passed to British ministers,” it said, adding that the GCHQ used what one document described as “ground-breaking intelligence capabilities” to intercept the communications of visiting delegations.

Tactics

The tactics included setting up internet cafes where they used an e-mail interception programme and key-logging software to spy on delegates’ use of computers; penetrating the security on delegates’ BlackBerrys; and supplying intelligence analysts with a live round-the-clock summary of who was phoning who at the summit.

The Turkish Finance Minister and possibly 15 others in his party were among those targeted while in a separate operation U.K.-based American spies intercepted top-secret communication of Mr. Medvedev.

“The details of the intercept were set out in a briefing paper prepared by the National Security Agency… and shared with high-ranking officials from Britain, Australia, Canada and New Zealand,” it said.

American intelligence agencies also reportedly planned to spy on delegates to the Commonwealth Heads of Government Meeting (CHOGM) in Trinidad in 2009.

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