A group of supporters of Venezuelan President Nicolas Maduro on Wednesday entered the opposition-dominated National Assembly, taking out their aggression on members of the opposition.

The rumpus ensued as an assembly session was held to mark Venezuela's independence day. Small explosions were heard initially, as fireworks were set off in the inner courtyard of the neoclassical parliament building.

Intruders seen carrying sticks and wearing red - the color of Maduro and his supporters - reached the corridors of the congressional building itself.

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Lawmakers and their assistants, as well as journalists, were also attacked. At least five people were said to have been hurt, with one taken away for medical treatment.

Deputies barricaded themselves in the chamber while the trouble unfolded.

One badly injured lawmaker was Popular Will party deputy Armando Armas, who tweeted: "Today the dictatorship tried to seize the sovereignty of the people. Here we are carrying on and we will keep on carrying on. They cannot do it with those people who shout FREEDOM!"

Fearless People's Alliance deputy Richard Blanco accused the mayor of Caracas Jorge Rodriguez of paying the instigators of the attack. He also blamed the military police, who have responsibility for guarding the legislative seat, of allowing the attack by groups known as "collectives."

"The responsibility is that of Colonel (Vladimir) Lugo, of the National Guard, who allowed collectives with sticks, knives and fireworks to enter a national seat of power and attack journalists and deputies. This is what is happening in Venezuela."

Blanco later tweeted: "There are seriously injured colleagues. It is now that we must carry on. For our part, we will not leave things this way. We will emerge from this disaster."

President Maduro condemned the attack, and ordered an investigation.

"I completely condemn these acts from what I know so far, I will never be complicit in any act of violence. I condemn them, and I order that they be investigated and that justice be done," Maduro said.

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The storming of the parliament came amid three months of often-violent confrontations between security forces and protesters. The demonstrators accuse the government of trying to establish a dictatorship by imprisoning opponents, sidelining the opposition-controlled assembly and redrafting the constitution to avoid fair elections.

Tensions had already been high on the morning of the attack as Vice President Tareck El Aissami made an unannounced morning visit to the legislature for the independence day event, making the case for constitutional changes.