A police officer and a civilian have been killed in a clash between residents of a Caracas neighbourhood and armed men who tried to remove a barricade, Venezuelan officials say.
Thursday's deaths brought to 20 the toll from a month of anti-government demonstrations in the divided South American country.
Witnesses said the shots came from a crowd of protesters. But Diosdado Cabello, president of the National Assembly, blamed "snipers" positioned on top of a building.
He identified the National Guards member as 25-year-old Acner Isaac Lopez Lyon, and said that motorcycle taxi driver, Jose Gregorio Amaris, was also killed while removing debris from the road.
Both were apparently shot on Thursday morning after area residents began banging pots and throwing bottles at people taking down a street barricade.
The opposition accuses the government of using armed civilian groups on motorcycles to break up demonstrations. Just before the deaths were announced, the country's chief prosecutor said the death toll from the protests stood at 19. Barricades of garbage, furniture and burning tyres have become a daily occurrence, holding up traffic in cities.
In a televised speech at a new government apartment building attended by the US actor Danny Glover, President Nicolas Maduro said the motorcyclist was removing debris so he could go about his job.
After he was shot, the National Guard arrived to secure the area and Lopez Lyon was killed. Maduro said a second motorcyclist was also seriously injured.
"Where are the opposition politicians to condemn these events, to search for peace like we're searching?" Maduro asked.
He called those building the barricades "vandals who hate the people".
In another development, Maduro called for a meeting of South American leaders on the turmoil in his country.
Maduro made the request on Thursday to visiting Suriname President Desi Bouterse, the current head of the Union of South American Nations (UNASUR).
The move came a day after Maduro broke off relations with Panama following its call for a meeting of the rival Washington-based Organisation of American States on the crisis.
Maduro said he wanted a UNASUR meeting convened so he could to explain "the attacks, the violence, the small groups that have tried to undermine social life and impose a political situation that our country is overcoming".
In a speech on Wednesday, Maduro rejected OAS involvement, saying Venezuela would turn to other regional organisations that do not include the US.
The OAS scheduled a closed-door meeting for later on Thursday to consider a request by Panama for a foreign ministers' meeting on Venezuela.
In Havana, Bruno Rodriguez, Cuba's foreign minister, denounced the "attempts at interference" by the OAS and the US.
"Venezuela has every right to defend its independence and sovereignty," he said, pledging Cuba's unyielding support for the Maduro government in the face of attempts to overthrow it.
Cuba, Venezuela's closest ally, depends on Caracas for half its energy needs at preferential prices and provides it with 40,000 advisers and health-care workers.
Bolivia's President Evo Morales, another Maduro ally, said "one or two" UNASUR presidents did not want to convene an emergency summit, creating an obstacle because the group's by-laws require that all 12 of the group's member states agree.
Street protests erupted in Venezuela on February 4 and have continued every day since in the biggest challenge yet to Maduro's nearly year-old government.
Public anger over rampant crime, shortages of basic goods and arrests of protesters have prompted the unrest, which Maduro claims is part of a US-backed plot by "fascists" to destabilise his regime.