Republican senator Rand Paul has announced plans to sue US President Barack Obama over Edward Snowden's revelations of unlawful spying by the National Security Agency (NSA).

Paul said he is urging all US citizens with mobile phones to join a group action aimed at preventing Obama from "snooping on the American people".

Paul said the legal action is also aimed at protecting the Fourth Amendment to the US constitution, which prevents unreasonable searches and seizures, and sending a message to the US government that it cannot continue to access ordinary citizens' phone and email records without permission or a warrant.

Speaking on the Fox News television show Hannity on Friday, Paul said: "The question here is whether or not, constitutionally, you can have a single warrant apply to millions of people.

"So we thought, what better way to illustrate the point than having hundreds of thousands of Americans sign up for a class action suit."

The senator said the lead lawyer in the suit is Ken Cuccinelli, Virginia's former attorney general.

Paul added: "We're hoping with his help that we can get a hearing in court and ultimately get this class-action lawsuit - I think the first of its kind on a constitutional question - all the way to the Supreme Court.

"We think we can have security, that we can defend against terrorism - but that doesn't mean that every single American has to give up their privacy."

The US's secretive Foreign Intelligence Surveillance Court ruled on Friday that the NSA can continue to collect US citizens' phone data for at least another 90 days despite a panel of experts advising President Obama that a warrant must be obtained for each search.

US government lawyers have also moved to block a decision by US District of Columbia Judge Richard Leon that the NSA's data collection programme is unlawful and "almost Orwellian" in nature.