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Saturday's Stop Watching Us rally in the US capital attracted a slew of people concerned by the National Security Agency's mass surveillance programs and featured an appearance -- in words anyway -- by Edward Snowden, whose massive leak of agency documents touched off the current debate about national security and civil liberties.

"This is about the unconstitutional, unethical, and immoral actions of the modern-day surveillance state and how we all must work together to remind government to stop them," Snowden said in a statement read by Justice Department whistle-blower Jesselyn Raddack. "It's about our right to know, to associate freely, and to live in an open society."

Snowden continued with a warning to lawmakers: "We declare that mass surveillance has no place in this country...It is time for reform. Elections are coming and we're watching you."

The rally was backed by a coalition of more than 100 companies and advocacy groups, including the Electronic Frontier Foundation and the American Civil Liberties Union, as well as individuals, such as Web inventor Tim Berners-Lee and Reddit founder Alexis Ohanian.

Speakers at the event included Rep. Justin Amash (R- Mich.); earlier NSA whistle-blower Thomas Drake; author Naomi Wolf; security specialist Bruce Schneier; and Gary Johnson, former governor of New Mexico and 2012 Libertarian party candidate for president, among others.

USA Today reported that thousands of people showed up for the demonstration and march, which moved from Washington, DC's Union Station to the Capitol Building. And the UK's Guardian newspaper, which has published many of the revelations drawn from the trove of Snowden documents, characterized the crowd as "featuring groups from the left and right of the political spectrum." (At one point Wolf found time to tweet, "I thanked a DC police officer for his service along the rally route and am so pleased he said thank you for being here, meaning all of us.")

The NSA, of course, defends its surveillance by saying it's essential in the fight against terrorism and for keeping an eye on foreign rivals.

Click the headline below to check out a selection of photos that participants in the demonstration posted to Twitter during the event.

We also have a Q&A with the rally's lead organizer, Rainey Reitman, activism director at the Electronic Frontier Foundation, and here's the complete Snowden statement that was read at the rally: