Tensions were already high after Vice President Tareck El Aissami made an unannounced morning visit to the National Assembly, accompanied by top government and military officials, for an event celebrating independence day.

The short appearance at the congress by top officials who have repeatedly dismissed the legislators as a band of U.S.-backed conspirators was seen by many as a provocation.

El Aissami said global powers are once again trying to subjugate Venezuela. "We still haven't finished definitively breaking the chains of the empire," he said, adding that President Nicolas Maduro's plans to rewrite the constitution — a move the opposition sees as a power-grab — offers Venezuela the best chance to be truly independent.