Polticians injured in Venezuela as government supporters storm congress.

Opposition politician Americo De Grazia is taken away on a stretcher after he was injured when a group of government supporters burst into Venezuela's opposition-controlled congress in Caracas, Venezuela on July 5, 2017. Carlos Garcia Rawlins / ReutersShow less

CARACAS  //  Pro-government militias wielding wooden sticks and metal bars stormed congress on Wednesday and began attacking opposition politicians during a special session coinciding with Venezuela's independence day.

Four congress members were injured. One of them, Americo de Grazia, had to be stretchered  to an ambulance suffering from convulsions..

"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 perceived enemies, pushing aside the legislature  - which is controlled by the opposition - 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 congress building, 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 were once again trying to subjugate Venezuela.

"We still haven't finished definitively breaking the chains of the empire," Mr El Aissami 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.

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

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

Later Mr 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 5-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  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 president Nicolas Maduro and his "assassin" allies.

Mr Perez gave no other details but pledged to join young protesters who have taken to the streets in the past three months against Mr Maduro.

"Stop talking. Get on the streets. Take action. Fight," he said in the video, sitting before a Venezuelan flag, with what appeared to be an assault rifle by his side. He also denounced Mr 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 June 27 attack shocked Venezuelans who had grown accustomed to almost-daily clashes since April between often-violent young protesters and security forces that have left more than 90 people dead and hundreds injured.

Mr 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 president Maduro claimed Mr Perez had stolen the helicopter because he was on an American-backed mission to oust him from power, many in the opposition questioned whether the incident was  staged by the government to distract attention from the president's increasingly authoritarian rule.

Adding to the intrigue is Mr Perez's colourful past.

In 2015, he produced and starred in a film called "Suspended Death," and several photos show him in fatigues, scuba diving while toting an assault rifle, skydiving and standing in action poses with a German shepherd dog at his side. In his political debut, he read a manifesto in which he claimed to be part of a group of disgruntled members of Venezuela's security forces who were determined to save the country's democracy.

Mr Maduro said a massive loss of life was avoided because Venezuela's air defense system was quickly activated. But in the video Mr Perez said  the strike produced no casualties because he had taken care to avoid them.

Neither of the buildings he attacked suffered damage. The helicopter he stole was found 24 hours later, abandoned in a verdant valley outside Caracas,  near the Caribbean coastline.

"They are going to have to put the entire nation in jail to stop our mission," he said in the new video. Within a few hours of release, it had been viewed online 135,000 times..