Thousands gathered by the Capitol reflection pool in Washington on Saturday to march, chant, and listen to speakers and performers as part of Stop Watching Us, a gathering to protest "mass surveillance" under NSA programs first disclosed by the whistleblower Edward Snowden.

Billed by organizers as "the largest rally yet to protest mass surveillance", Stop Watching Us was sponsored by an unusually broad coalition of left- and right-wing groups, including everything from the American Civil Liberties Union, the Green Party, Color of Change and Daily Kos to the Libertarian Party, FreedomWorks and Young Americans for Liberty.

The events began outside Union Station, a few blocks away from the Capitol. Props abounded, with a model drone hoisted by one member of the crowd and a large parachute carried by others. One member of the left-wing protest group Code Pink wore a large Barack Obama mascot head and carried around a cardboard camera. Organizers supplied placards reading "Stop Watching _____", allowing protesters to fill in their own name – or other slogans and occasional profanities. Homemade signs were more colorful, reading "Don't Tap Me, Bro" "Yes, We Scan" and "No Snitching Allowed".

"They think an open government means our information is open for the taking," David Segal of Demand Progress, an internet activist group, said to kick off events. As the march proceeded from Union Station to the Capitol reflecting pool, the crowd sang various chants, from "Hey hey, ho ho, mass surveillance has got to go" to "They say wire tap? We say fight back!"

David Reed, of Maryland, said he felt compelled to show up because of the "apathy" he sees among much of the public towards whistleblowers. Reed said he attended the trial of Chelsea Manning, the military whistleblower who leaked thousands of State Department cables to Wikileaks, as an observer, and was "disappointed that so few people showed up".

"The courtroom only held about 30 people, and there were few days that it was filled up," said Reed, who described himself as "just a concerned citizen". "We just stand by and watch."

A protester wears a mask depicting a skull beneath the head of the Statue of Liberty, beneath a model of a US drone aircraft. Photograph: Jonathan Ernst/Reuters

The program at the reflecting pool included ex-politicians, whistleblowers, professional activists, poets and a punk band, YACHT, who performed their song Party at the NSA. ("Party at the NSA/Twenty-twenty-twenty-four hours a day!")

Thomas Drake, the former NSA official who blew the whistle on government surveillance and waste following 9/11 and was charged under the Espionage Act, was on hand, talking to reporters about, among other things, recent revelations that the US government had tapped the phone of the German chancellor, Angela Merkel, and other world leaders.

"For what? Why would you violate her rights? Because, what, she might know something about terrorism?" he said. "What is that all about? They're an ally! They're partnered with us. I mean there are threats to the international order and stability. Why would you breach the trust of the chancellor of Germany?"

When Drake addressed the crowd, he said any domestic surveillance legislation that might result from the Snowden leaks "must include whistleblower protection", because "without adequate protections, [government employees] are more likely to turn a blind eye" to abuses of power. He warned against the "acid turned up by the potent brew of secrecy and surveillance".

Another well-received speaker, Gary Johnson, the former governor of New Mexico and 2012 Libertarian party candidate for president, said "there's only one way to fix the Patriot Act: and that's to repeal the Patriot Act". He too was concerned about the apathy towards surveillance programs that comes when someone thinks it's "not about me".

Demonstrators hold placards supporting Edward Snowden. Photograph: Mandel Ngan/AFP/Getty Images

But the big star of the day, despite his physical absence, was Edward Snowden – "Thank you, Edward Snowden" was the most popular banner slogan among the cord. Jesselyn Radack, a former Justice Department ethics advisor who is now a director with the Government Accountability Project, read a statement from Snowden to the crowd.

"This isn't about red or blue party lines, and it definitely isn't about terrorism," Snowden wrote. "It's about being able to live in a free and open society." He also noted that "elections are coming up, and we are watching you". Members of Congress and government officials, he said, were supposed to be "public servants, not private investigators".

William Evans, of Richmond, Virginia, may have best embodied the nonpartisan atmosphere and message of the event. He wore a "Richmond Tea Party" baseball cap, as well as a Code Pink sticker saying "Make Out, Not War". He is a member of the Richmond Tea Party but not of Code Pink, he said, adding that he "just loved" what the sticker said. Evans said he was attending to protest the "shredding of the constitution" and added that he was happy that "you guys on the left are finally starting to see it".

"We may not always agree on our belief system," he added, "but thank God we agree on the constitution."