PHILADELPHIA -- When Bernie Sanders offered his official nomination of Hillary Clinton for the presidency Tuesday evening, dozens of 'Bernie or Bust' delegates rejected the Vermont senator's convention floor concession.

Even as Sanders called to "move that Hillary Clinton be selected as the nominee of the Democratic party," his devotees staged a disruptive walk-out from the convention floor, marching through the Wells Fargo Center arena and plunking down at a media tent outside.

Bernie Sanders fans are staging a walkout now after Hillary Clinton is nominated #DemsInPhilly pic.twitter.com/HTBrmcK6x7 — MJ Lee (@mj_lee) July 26, 2016

Here's the flyer Bernie delegates got pic.twitter.com/bojwl3Z1rE — Emma Roller (@emmaroller) July 26, 2016

Bernie walkout has turned into a mostly silent sit-in. #DemsInPhilly pic.twitter.com/J15MosdSM2 — MJ Lee (@mj_lee) July 26, 2016

There are around 1900 Bernie delegates; looks like 150 or so walked out, obscured by media. pic.twitter.com/jQlrbDHN1l — daveweigel (@daveweigel) July 26, 2016

About 25 protesters refused to move from the floor of the media tent. After police cordoned off access to the space, over a hundred more congregated outside.

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The demonstrators linked arms, duct-taped their mouths shut to signify their votes had been "silenced" at the convention, and held up signs with phrases like "The revolution continues" and "#DemExit."

Outside the Bernie or bust storming of media row #DNCinPHL #DNCDisaster pic.twitter.com/4yviTGycwu — Cassandra Fairbanks (@CassandraRules) July 26, 2016

Later in the evening, while protesters seemed to try blocking delegates from exiting, police in riot gear converged just inside convention perimeter. The officers lined up against the inside of the fence in case the protestors break through.

In Philadelphia's downtown, some Sanders supporters headed to protest outside of city hall, according to CBS News' Jacqueline Alemany.

Some activists burned American flags during their demonstration:

Demonstrators burn a flag during a protest in Philadelphia, Tuesday, July 26, 2016, during the second day of the Democratic National Convention. AP

Marchers now burning a few American flags #DemsInPhilly pic.twitter.com/vcKF4MgE3D — Bobby Allyn (@BobbyAllyn) July 27, 2016

According to The Associated Press, "Some Sanders backers started scaling 8-foot walls that blocked off the secure zone around the arena parking lot. Police and the Secret Service immediately arrested four protesters, who will be charged with entering a restricted area. They're scheduled to appear in court Wednesday.

"Protests continued into the night as Sanders supporters and an anti-police brutality group joined together. Later, another protester set an Israeli flag on fire as people chanted, "long live the intifada." Others then came together for a candlelight vigil."

CBS News' Sean Gallitz and Jacqueline Alemany contributed to this report.