Millions of Cubans took to the streets on Wednesday in protest over new sanctions imposed on the Caribbean island by the Trump administration and U.S. efforts to topple the government of socialist ally Venezuela, reports Reuters.

“We will give a strong, firm and revolutionary response to the statements loaded with threats, provocations, lies and slander of the Yankee empire,” tweeted Cuban President Miguel Diaz-Canel as dawn broke over Havana.

The annual marches across the Communist-run country, marking International Workers Day, provided the first opportunity to publicly protest a U.S. offensive against socialism in the region declared by U.S. national security advisor John Bolton late last year. That was followed by a series of new sanctions against Venezuela, Cuba and Nicaragua and the appearance of shortages of basic goods on the island.

“We denounce the maneuvers aimed at destabilizing the left and progressive governments, particularly in Venezuela and Nicaragua,” according to a statement read at the start of the march in Havana’s historic Revolution Plaza.

On Tuesday, Trump threatened a "full and complete embargo here" and more sanctions if Cuban troops continued to prop up the Venezuelan government of socialist President Nicolas Maduro. Those remarks came after Bolton said there were more than 20,000 Cuban military personnel in Venezuela and that potential high-level defectors feared Cuba’s wrath.

“Bolton is a pathological liar who misinforms President Trump. There are no Cuban troops in Venezuela or Cubans participating in military or security operations,” Cuban Foreign Minister Bruno Rodriguez tweeted on Tuesday.