BERLIN - The US National Security Agency (NSA) bugged the video conferencing system at the UN headquarters in New York and cracked its encryption, German weekly Der Spiegel reported Sunday.

The tapping scheme succeeded in the summer of 2012, the magazine said, citing secret documents disclosed by former US intelligence contractor Edward Snowden.

The move offered the NSA "a dramatic improvement of data on video conferencing and the ability to decrypt that data", a quoted document said, noting that the number of decrypted communications jumped from 12 to 458 within three weeks.

Der Spiegel also reported that the US intelligence agency spied on the European Union mission after it moved to its new embassy in New York last September.

The new embassy's plans, as well as its IT infrastructure and servers, were among the copies of relevant NSA documents provided Snowden.

According to the documents analyzed by the weekly, the NSA also ran a monitoring program covering more than 80 embassies and consulates worldwide.

The program was called "the Special Collection Service" and operated without the knowledge of the host country, said the magazine.

NSA documents urged to keep the existence of the program as a secret at all costs, as "relations with the host country would be seriously damaged" if it was leaked, Der Spiegel reported.

Revelations about PRISM and other surveillance programs that obtain personal information by hacking phone calls and emails have embarrassed Washington and triggered outrage around the world.

Some EU privacy watchdogs are demanding an independent investigation into the extent of PRISM as well as other platforms used by the NSA.

US President Barack Obama defended the spying program as a "modest encroachment" on privacy necessary to prevent terror attacks, but pledged to overhaul US surveillance and turn it more transparent.