Venezuelan troops on Thursday fired what appeared to be rubber bullets at protesters as they attacked the perimeter of an airbase, killing a demonstrator and bringing the death toll to at least 76 in unrest since April.

At least two soldiers shot long firearms through the fence at protesters from a distance of just a few metres. One man collapsed to the ground and was carried off by other demonstrators, television footage showed. Paramedics took at least two other wounded people to a hospital, a witness told Reuters news agency.

The protesters began attacking the fence outside La Carlota airbase in the wealthy east of Caracas when security forces broke up a march destined for the attorney general's office.

Hundreds of thousands of Venezuelans have taken to the streets over the past months to protest against a clampdown on the opposition, shortages of food and medicine, and President Nicolas Maduro's plan to overhaul the constitution.

READ MORE: Venezuela - What is happening today?

Maduro says the violence is part of a foreign-led plot to overthrow his government.

A man identified as David Jose Vallenilla, 22, died after arriving at a hospital in the Chacao municipality where the protest happened, the mayor said.

"He died at a private clinic where he arrived in very bad condition," said Mayor Ramon Muchacho.

Speaking outside the clinic, opposition politician Jose Manuel Olivares said Vallenilla had been killed by the national guard firing rubber bullets at point-blank range and criticised the shooting as repression.

Colombians seek escape at home amid Venezuela’s crisis

"The troops found responsible for crimes will be presented before the law," said Interior Minister Nestor Reverol, calling on the opposition to stop violent demonstrations.

Venezuela's national guard is a wing of the military charged with internal public order. It mainly uses tear gas, water cannon and rubber bullets to control protests that frequently escalate into riots.

Despite volleys of tear gas and rubber bullets, a small group of demonstrators throwing petrol bombs and powerful fireworks from behind flimsy homemade shields was able to rip down a section of the fence surrounding the airbase.

On Monday, a teenager died during another protest in the same area. Footage of the demonstration showed a national guard soldier pointing a pistol at protesters.

The government is investigating troops involved in that incident. "I have ordered an investigation to see if there was a conspiracy behind this," Maduro said earlier on Thursday, saying the men involved in Monday's shooting had been detained.

US envoy urges global action on crisis

Meanwhile, US Ambassador Nikki Haley on Thursday urged the international community to take action to deal with the worsening crisis in Venezuela.

"The tragic situation in Venezuela calls out for action," Haley said in a statement in which she complained about the lack of action from the UN Human Rights Council and the Organization of American States. "The Venezuelan people are starving while their government tramples their democracy."

READ MORE: Venezuela's worst economic crisis - What went wrong?

Maduro's government has rejected US calls for action by the international community. In a press conference from Caracas, Maduro pointed to a statement signed by 57 countries - including China, Russia and South Africa - supporting his socialist government and opposing any interference in the country's internal affairs.

"The imperialists have a fatal obsession with us," Maduro said. "We're not going to permit that they turn us into a martyr or that the world crucifies Venezuela."

Don't blame socialism for Venezuela's woes - UpFront Reality Check

Source: News agencies