A National Security Agency (NSA) data gathering facility is seen in Bluffdale, about 25 miles (40 kms) south of Salt Lake City, Utah, in this file photo taken December 17, 2013.[Photo/Agencies]

NEW YORK/WASHINGTON - The US National Security Agency was sued on Tuesday by Wikimedia and other groups challenging one of its mass surveillance programs that they said violates Americans' privacy and makes individuals worldwide less likely to share sensitive information.

The lawsuit filed in federal court in Maryland, where the spy agency is based, said the NSA is violating US constitutional protections and the law by tapping into high-capacity cables, switches and routers that move Internet traffic through the United States.

The case is a new potential legal front for privacy advocates who have challenged US spying programs several times since 2013, when documents leaked by former NSA contractor Edward Snowden revealed the long reach of government surveillance.

Other lawsuits have challenged the bulk collection of telephone metadata and are pending in US appeals courts.

The litigation announced on Tuesday takes on what is often called "upstream" collection because it happens along the so-called backbone of the Internet and away from individual users.

Bulk collection there violates the constitution's First Amendment, which protects freedom of speech and association, and the Fourth Amendment, which protects against unreasonable search and seizure, the lawsuit said.

The plaintiffs include the Wikimedia Foundation, which runs the online encyclopedia Wikipedia, the conservative Rutherford Institute, Amnesty International USA and the National Association of Criminal Defense Lawyers, among other groups.

The groups said in the lawsuit that upstream surveillance "reduces the likelihood" that clients, journalists, foreign government officials, victims of human rights abuses and other individuals will share sensitive information with them.

Legal standing, which requires the organizations to show individual, particular harm, is the most significant obstacle for them, said Stephen Vladeck, a professor at American University Washington College of Law.

While it might stand to reason that the plaintiffs' communications are being intercepted, they can only use legally public information, which the government has acknowledged or declassified, to show harm, Vladeck said. It is "not beyond the pale" that the government could make more information public while the lawsuit is pending, he said. For now, the lawsuit is a "longshot" according to Vladeck.

An Obama administration official said: "We've been very clear about what constitutes a valid target of electronic surveillance. The act of innocuously updating or reading an online article does not fall into that category."

The US Department of Justice, which was named as a defendant along with the NSA, said it was reviewing the lawsuit. The NSA did not immediately respond to requests for comment.

"By tapping the backbone of the Internet, the NSA is straining the backbone of democracy," Lila Tretikov, executive director of the Wikimedia Foundation, said in a statement.