NSA Chief Says Data Disrupted ‘Dozens’ Of Plots

The head of the US electronic spying agency has defended the massive surveillance programmes newly revealed by a former intelligence worker.

In a US Senate hearing, National Security Agency (NSA) Director Keith Alexander said the programmes had disrupted dozens of terror plots.

And US Secretary of State John Kerry said they showed a "delicate but vital balance" between privacy and security.

Meanwhile, the leaker has pledged to fight extradition to the US.

Edward Snowden fled his home in Hawaii for Hong Kong shortly before reports of top secret programmes were published by the Guardian and Washington Post newspapers last week.

The 29-year-old former CIA and NSA contract worker has admitted giving the newspapers information about NSA programmes to seize vast quantities of data on telephone calls and internet communications from US internet and telephone companies.

US officials have confirmed the programmes exist, with President Barack Obama saying they were overseen by Congress and the courts.

'Compliance and oversight'

And officials have defended the programmes as vital national security tools.

"It's dozens of terrorist events that these have helped prevent," Gen Alexander said on Wednesday at a hearing of the US Senate intelligence committee.

And he backed the workers who run the programmes.

"Our nation has invested a lot in these people. They do this lawfully. They take compliance oversight, protecting civil liberties, privacy and security of this nation to their heart every day," he said.

But Gen Alexander said the agency needed to investigate how Mr Snowden, a relatively low-ranking contract employee, had been able to obtain and leak such sensitive information.

The processes "absolutely need to be looked at," he told lawmakers.

"In the IT arena, in the cyber arena, some of these folks have tremendous skills to operate networks."

The information leaked by Mr Snowden has undoubtedly angered the US government, but so far he has not been charged by the authorities, nor is he the subject of an extradition request.

European leaders have also expressed concerns over the scale of the programmes and have demanded to know whether the rights of EU citizens had been infringed.

Meanwhile, in a news conference alongside UK Foreign Secretary William Hague, Mr Kerry said: "With respect to privacy, freedom and the constitution I think over time, this will withstand scrutiny and people will understand it."