Washington: Two phone and Internet surveillance programmes run by the US National Security Agency (NSA) helped disrupt over 50 potential terrorist attacks against the US and its allies, the agency's chief said.

Two classified programmes, one collecting US phone records and the other mining Internet data, were revealed last week after leaks from defense contractor Edward Snowden. The Congress panel hearing on Tuesday was the first of its kind dedicated to the recent disclosures of the phone and Internet surveillance programmes by the NSA.

Army General Keith Alexander, the director of the National Security Agency and commander of US Cyber Command, defended the recently revealed surveillance programmes before members of the House of Representatives Intelligence Committee.

During the hearing, Alexander and officials from the FBI and the Office of the Director of National Intelligence provided details of a plot to blow up the Stock Exchange in New York.

"Let me start by saying that I would much rather be here today debating this point than trying to explain how we failed to prevent another 9/11," said Alexander, while stressing that these two programmes have held great value to national security and their allies in combating terrorism.

"In recent years, these programmes, together with other intelligence, have protected the US and our allies from terrorist threats across the globe to include helping prevent the terrorist attacks over 50 times since 9/ 11," he claimed.

The plots included a previously undisclosed plan to blow up the New York Stock Exchange, Alexander added and noted the Sep. 11 attacks in 2001 occurred in part because of a failure on the part of the government to connect those dots, some of which were already in the country.

The four-star general also told members that agency officials planned to provide them with an unclassified summary of the foiled terror plots to Congress by Wednesday.


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