Elon Musk posted a cryptic message about the "No Kings" protests after activists took to the streets across the U.S. over the weekend.

Millions of people across the country are expected to join in protest this weekend against Donald Trump’s administration, a movement intended to coincide with the president’s planned military parade in Washington — and the commander-in-chief’s 79th birthday.

The “No Kings” rallies were organized in nearly 2,000 locations nationwide, including cities, towns, and community spaces.

"No Kings" protests against President Donald Trump’s policies are scheduled in nearly 2,000 cities across the U.S. Saturday as a military parade rolls in Washington for the Army’s 250th anniversary – which is also Flag Day and Trump’s birthday.

Sellers are hawking Army anniversary and "No Kings" T-shirts, hats and other items in a move to cash in on Saturday's military parade and anti-Trump protests.

Protests are underway in Jacksonville and across the United States as part of the "No Kings" nationwide day of defiance. Watch live coverage here.

Part of a national day of mobilization, the protests were scheduled the same day as President Trump's military parade in Washington, D.C.

A flagship "No Kings" march and rally are planned in Philadelphia, but no events are scheduled to take place in Washington, D.C., where the military parade will take place on Trump's 79th birthday. Organizers of the protests say they want to take attention away from the parade.