The US National Security Agency broke the encryption securing the United Nations' internal video conferencing at its New York headquarters, the German news weekly Der Spiegel reported yesterday, citing secret NSA documents.
The NSA, on one occasion, also allegedly caught the Chinese secret services eavesdropping on the UN in 2011, it added.
It said the NSA, which for months has been at the centre of revelations by intelligence leaker Edward Snowden, broke the encryption in the summer of last year and within nearly three weeks, had bumped up the number of decrypted communications from 12 to 458.
The move provided the agency with "a dramatic improvement of data from video teleconferences and the ability to decrypt this data traffic", the magazine quoted an NSA document as saying.
Der Spiegel also claims that the US agency kept tabs on the European Union after it moved into new offices in New York in September 2012. Among documents provided by Snowden were plans of the EU's premises, which the NSA codenamed "Apalachee".
Earlier reports in Der Spiegel and Britain's The Guardian newspaper had detailed alleged widespread covert surveillance by the NSA of EU offices, including diplomatic missions in Washington and at the UN in New York, as well as at the 28-member bloc's Brussels headquarters.
The US administration has scrambled to defend spying programmes in the wake of the leaks by Snowden, a former IT contractor at the NSA.