Edward Snowden has hailed landmark shifts in Congress and the US courts on NSA surveillance but cautioned that much more needs to be done to restore the balance in favour of privacy.

He also warned this was only the beginning of reform of the NSA, saying there are still many bulk collection programmes which are "even more intrusive", but expressed hope that the Senate would act to curb the NSA, saying retention of the status quo is untenable.

In an hour-long interview with the Guardian in Moscow, the NSA whistleblower said the moves by the federal court and the House of Representatives marked the first time since the 1970s there had been a reduction rather than expansion in the powers of the surveillance agencies.

"In our modern era, that is without precedent," he said.