US admits electronic spying on Americans was illegal The court concluded the program violated privacy rights enshrined in the Fourth Amendment to the US Constitution. The surveillance resulted "in the acquisition of a very large number of Fourth Amendment-protected communications that have no direct connection to any targeted facility and thus do not serve the national security needs" defined under the law, the court said. The government altered the program and later came back to the court for approval of a revised surveillance operation. A senior US official, who spoke to reporters on condition of anonymity, played down the surveillance violation as "a technological problem" rather than an intentional invasion of privacy. "These documents released today will provide a strong indication to back up the statements we've been making from the beginning about the strong nature of the oversight of this program," said the official. "This is not an egregious overreaching," he said, adding it was merely "an inadvertent problem that involved a relatively small number of US persons." But the court, in its ruling, disagreed with the government's claim the collection was inadvertent and demanded the NSA change the program. Citing the declassified documents, rights advocates expressed alarm at the scale of the surveillance and said the government had to do more to reassure the public. "The FISA court opinion released today serves as further confirmation that the NSA is tapping the domestic Internet backbone," the Center for Democracy and Technology, a think tank, said in a tweet. Democratic Senator Mark Udall - a long-time critic of the surveillance programs -welcomed the NSA's decision to reveal the details of the episode but said more protections were needed to safeguard civil liberties. "I am glad the NSA is taking this step at owning its mistakes, but it is also a sign that we can and must do more to protect innocent Americans with no connection to terrorism from being monitored by our government - whether intentionally or not," Udall said. The government's biggest challenge was to restore the public's trust, said Sascha Meinrath, director of the Open Technology Institute. "It's time for the Obama administration to come clean about the full scope of its activities," Mr Meinrath said in a statement. President Barack Obama has insisted that Americans' privacy rights are protected and that surveillance powers have not been abused in the search to uncover terror plots. The scope of America's massive electronic spying effort - which sweeps up Internet traffic and phone records - was exposed starting in June when news outlets reported on documents leaked to them by Mr Snowden. Mr Snowden is wanted by the United States on espionage charges over his leaks but has obtained temporary asylum in Russia.