WASHINGTON - More than 250 academics from around the world signed an online petition this week calling for an end to "blanket mass surveillance" by intelligence agencies.

The petition said revelations of mass surveillance in documents leaked by former US National Security Agency (NSA) contractor Edward Snowden violate "a fundamental right" protected by international treaties, including the International Covenant on Civil and Political Rights and the European Convention on Human Rights.

"This has to stop," said the petition (academicsagainstsurveillance.net), an initiative of four academics from the University of Amsterdam.

"Without privacy people cannot freely express their opinions or seek and receive information. Moreover, mass surveillance turns the presumption of innocence into a presumption of guilt... secret and unfettered surveillance practices violate fundamental rights and the rule of law, and undermine democracy.

"The signatories of this declaration call upon nation states to take action. Intelligence agencies must be subjected to transparency and accountability. People must be free from blanket mass surveillance conducted by intelligence agencies from their own or foreign countries."

The signatories include academics in the Netherlands, Britain, Germany and the United States.

Among them are Oxford University's Joss Wright, Alessandro Acquisti of Carnegie Mellon University, Aleecia McDonald of the Center for Internet & Society at Stanford University and Bruce Schneier of the Berkman Institute for Internet and Society at Harvard Law School.

Other signatories were from as far as Australia, Hong Kong and New Zealand.

On Thursday, a report indicated that the NSA is making strides toward building a "quantum computer" that could break nearly any kind of encryption.

The Washington Post said leaked documents from Snowden indicate the computer would allow the secret intelligence agency to break encryption used to protect banking, medical, business and government records around the world.

Quantum computing has been a goal among commercial firms such as IBM because it could harness the power of atoms and molecules, vastly increasing speed and security of computers and other devices.

Snowden leaked explosive details of the secret surveillance schemes to media including The Washington Post and The Guardian.

After fleeing the United States, he ultimately landed in Russia, where he has been granted temporary asylum. US federal prosecutors have filed a criminal complaint against Snowden, charging him with espionage and felony theft of government property.