Four Venezuelan politicians have been wounded after pro-government militias wielding wooden sticks and metal bars stormed the opposition-controlled Congress during a special session to mark the country’s independence day.

Blood was left splattered on the neoclassical legislature’s white walls. One of the wounded politicians, Americo de Grazia, had to be taken in a stretcher to an ambulance suffering from convulsions, said a fellow congressman.

“This doesn’t hurt as much as watching how every day how we lose a little bit more of our country,” Armando Arias said from inside an ambulance as he was being treated for head wounds that spilled blood across his clothes.

The attack, in plain view of national guardsmen assigned to protect the legislature, comes amid three months of often-violent confrontations between security forces and protesters who accuse the government of trying to establish a dictatorship by jailing foes, pushing aside the opposition-controlled legislature and rewriting the constitution to avoid fair elections.

Tensions were already high after vice-president Tareck El Aissami made an unannounced morning visit to the neoclassical legislature, accompanied by top government and military officials, for an event celebrating independence day.

Standing next to a display case holding Venezuela’s declaration of independence from Spain, he said global powers are once again trying to subjugate Venezuela.

“We still haven’t finished definitively breaking the chains of the empire,” El Aissami said, adding that 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.

After he left, dozens of government supporters set up a picket outside the building, heckling lawmakers with menacing chants and eventually invading the legislature themselves.

Despite the violence, lawmakers approved a plan by the opposition to hold a symbolic referendum on 16 July that would give voters the chance to reject Maduro’s plans to draft a new political charter.

Later Maduro condemned the violence, calling for a full investigation during a speech while attending a military parade.

The clash followed Tuesday’s appearance of a five-minute video posted by a former police inspector who allegedly stole a helicopter and fired on two government buildings last week.

Oscar Perez, repeating a call for rebellion among the security forces, said that he was in Caracas after abandoning the helicopter along the Caribbean coast and was ready for the “second phase” of his campaign to free his homeland from what he called the corrupt rule of Maduro and his “assassin” allies.

Perez gave no other details but pledged to join youth who have been protesting on the streets the past three months against Maduro.

“Stop talking. Get on the streets. Take action. Fight,” he said in the video, sitting before a Venezuelan flag and with what looks like an assault rifle by his side. He also denounced Maduro’s plan to rewrite the constitution.

“If this constitutional assembly goes through, Venezuela will cease to exist because we’ll have given away the country to the Cubans,” he said.

The bold, though largely harmless 27 June attack shocked Venezuelans who had grown accustomed to almost-daily clashes since April between often-violent youth protesters and security forces that have left more than 90 people dead and hundreds injured.

Perez apparently piloted the stolen police helicopter that sprayed 15 bullets toward the interior ministry and dropped at least two grenades over the supreme court building.

While Maduro claimed Perez had stolen the helicopter on a US-backed mission to oust him from power, many in the opposition questioned whether the incident was a staged by the government to distract attention from the president’s increasingly authoritarian rule.Adding to the intrigue is Perez’s colorful past.