美安全局G20峯會監視梅德韋傑夫

Leaked documents reveal Russian president was spied on during visit, as questions are raised over use of US base in Britain.

American spies based in the UK intercepted the top-secret communications of the then Russian president, Dmitry Medvedev, during his visit to Britain for the G20 summit in London, leaked documents reveal.

The details of the intercept were set out in a briefing prepared by the National Security Agency (NSA), America's biggest surveillance and eavesdropping organisation, and shared with high-ranking officials from Britain, Australia, Canada and New Zealand.

The document, leaked by the NSA whistleblower Edward Snowden and seen by the Guardian, shows the agency believed it might have discovered "a change in the way Russian leadership signals have been normally transmitted".

The disclosure underlines the importance of the US spy hub at RAF Menwith Hill in Harrogate, North Yorkshire, where hundreds of NSA analysts are based, working alongside liaison officers from GCHQ.

The document was drafted in August 2009, four months after the visit by Medvedev, who joined other world leaders in London, including the US president, Barack Obama, for the event hosted by the British prime minister, Gordon Brown.

Medvedev arrived in London on Wednesday 1 April and the NSA intercepted communications from his delegation the same day, according to the NSA paper, entitled: "Russian Leadership Communications in support of President Dmitry Medvedev at the G20 summit in London – Intercept at Menwith Hill station."

The document starts with two pictures of Medvedev smiling for the world's media alongside Brown and Obama in bilateral discussions before the main summit.

The report says: "This is an analysis of signal activity in support of President Dmitry Medvedev's visit to London. The report details a change in the way Russian leadership signals have been normally transmitted. The signal activity was found to be emanating from the Russian embassy in London and the communications are believed to be in support of the Russian president."

The NSA interception of the Russian leadership at G20 came hours after Obama and Medvedev had met for the first time. Relations between the two leaders had been smoothed in the runup to the summit with a series of phone calls and letters, with both men wanting to establish a trusting relationship to discuss the ongoing banking crisis and nuclear disarmament.

In the aftermath of their discussions on 1 April, the two men issued a joint communique saying they intended to "move further along the path of reducing and limiting strategic offensive arms in accordance with the treaty on the non-proliferation of nuclear weapons".

A White House official who briefed journalists described the meeting as "a very successful first meeting focused on real issues". The official said it had been important for the men to be open about the issues on which they agreed and disagreed. Obama had stressed the need to be candid, the official noted.

While it has been widely known the two countries spy on each other, it is rare for either to be caught in the act; the latest disclosures will also be deeply embarrassing for the White House as Obama prepares to meet Vladimir Putin, who succeeded Medvedev as president, in the margins of the G8 summit this week.

The two countries have long complained about the extent of each other's espionage activities, and tit-for-tat expulsions of diplomats are common. A year after Obama met Medvedev, the US claimed it had broken a highly sophisticated spy ring that carried out "deep cover" assignments in the US.

Ten alleged Russian spies living in America were arrested.

Putin was withering of the FBI-led operation: "I see that your police have let themselves go and put some people in jail, but I guess that is their job. I hope the positive trend that we have seen develop in our bilateral relations recently will not be harmed by these events." Last month, the Russians arrested an American in Moscow who they alleged was a CIA agent.

The new revelations underline the significance of RAF Menwith Hill and raise questions about its relationship to the British intelligence agencies, and who is responsible for overseeing it. The 560-acre site was leased to the Americans in 1954 and the NSA has had a large presence there since 1966.

It has often been described as the biggest surveillance and interception facility in the world, and has 33 distinct white "radomes" that house satellite dishes. A US base in all but name, it has British intelligence analysts seconded to work alongside NSA colleagues, though it is unclear how the two agencies obtain and share intelligence – and under whose legal authority they are working under.據英國《衛報》6月16日報道，有泄露的文件披露，美國駐英間諜在俄羅斯總統德米特里·梅德韋傑夫2009年赴倫敦出席G20峯會期間監聽他的絕密通信。

美國國家安全局是美國最大的監視和竊聽機構、美國國家安全局在簡報中與英國、澳大利亞、加拿大和新西蘭的高官分享了監聽細節。

《衛報》所看到的泄密文件由愛華德·斯諾登提供，該文件顯示，美國國家安全局認爲其可能發現了俄領導層在慣常的信號傳達方式上的變化。

文件起草於2009年8月。4個月前，梅德韋傑夫、美國總統巴拉克·奧巴馬和其他國家領導人一起在倫敦出席英國首相布朗主持的峯會。

據美國國家安全局的文件，梅德韋傑夫於4月1日抵達倫敦，美國國家安全局當天就截獲了其代表團的通信。文件名爲：“倫敦G20峯會上俄領導人德米特里·梅德韋傑夫總統的通訊支持——截獲於曼威斯山站。”

文件的開頭是照片上是梅德韋傑夫笑容滿面地分別與布朗和奧巴馬會談的兩張照片。

報告稱：“這是一份對德米特里·梅德韋傑夫總統倫敦之行的信號活動分析。本報告詳述了俄羅斯領導層在信號傳輸方式上的變化。信號從俄羅斯駐英國大使館傳出。”美國國家安全局截獲的俄領導人通訊是在奧巴馬和梅德韋傑夫第一次會見幾小時之後。

雖然，美俄兩國互相監視已是衆所周知的事情，然而任何一方被當場抓住的情況還是很罕見；最新的爆料文件讓白宮感到十分尷尬，因爲奧巴馬準備在本週G8峯會期間和普京進行會見。

美俄長期以來互相指責對方間諜活動，且經常針鋒相對地驅逐外交官。在奧巴馬會見梅德韋傑夫一年之後，美國聲稱破獲了俄間諜網，說該間諜網在美國執行“深度潛伏”任務，並逮捕了10名生活在美國的俄羅斯人。

普京對此表示：“我看到你們警察把一些人投進了監獄，但我想這是他們的本職工作。我希望我們最近趨於改善的雙邊關係不會因此受到傷害。”而上月，俄羅斯人在莫斯科逮捕了一名美國人，稱他是一名美國中央情報局間諜。

這凸顯了曼威斯山英國皇家空軍基地的美國間諜中心的重要性。該基地位於英格蘭北約克郡哈羅蓋特，那裏駐有數百美國國家安全局分析師，和英國政府通信總部的聯絡官並肩工作。這塊560英畝（約3400畝）的基地在1954年被租給美國，美國國家安全局自1966年起就在那裏建有一個大型基地。

這裏被視爲世界上最大的監視和竊聽基地，有33處明顯的白色“雷達罩”。雖然尚不清楚這兩個機構如何獲取和分享情報，已有英國情報分析師在此與美國同行一起工作。