A lawsuit filed by the operator of Wikipedia and other organisations challenges the US government's mass online surveillance programs, claiming that tapping into the internet "backbone" is illegal.
The lawsuit was filed in Maryland Federal Court by the Wikimedia Foundation, Amnesty International USA, Human Rights Watch, and other organisations on Tuesday.
It said the effort by the National Security Agency (NSA) and other intelligence services "exceeds the scope of the authority that Congress provided", and violates US constitutional guarantees.
"We're filing suit today on behalf of our readers and editors everywhere," said Jimmy Wales, founder of Wikipedia, in a statement.
"Surveillance erodes the original promise of the internet: An open space for collaboration and experimentation, and a place free from fear."
The lawsuit claims that by tapping into the internet backbone, "the NSA is seizing Americans' communications en masse while they are in transit, and it is searching the contents of substantially all international text-based communications", effectively sweeping up data of many people unrelated to the effort to thwart terrorism.
"Rather than limit itself to monitoring Americans' communications with the foreign targets, the NSA is spying on everyone, trying to find out who might be talking or reading about those targets," said Patrick Toomey of the American Civil Liberties Union, which is representing the organisations.
"As a result, countless innocent people will be caught up in the NSA's massive net."
The lawsuit argues that based on documents leaked by former NSA contractor Edward Snowden, the NSA intercepts virtually all internet communications flowing across the network of high-capacity cables, switches, and routers that make up the internet backbone.