Venezuela is deploying troops in a western province bordering Colombia after a teenage boy was killed in overnight looting amid a wave of anti-government protests.

"I have ordered the transfer of 2,000 guards and 600 special operations troops" to the state of Tachira, Defence Minister Vladimir Padrino Lopez told state media on Wednesday.

Authorities said looting and attacks against security installations erupted overnight in the state, where three people have died this week, including 15-year-old Jose Guerrero.

The teenager was shot dead during Wednesday's spate of looting in San Cristobal, his relatives said.

"My mom sent my brother yesterday to buy flour for dinner and a little while later, we received a call saying he'd been injured by a bullet," his sister, Maria Contreras, told the Reuters news agency.

The state prosecutor's office confirmed his death, which pushed the death toll in six weeks of unrest to at least 43, matching the number of people killed in the last comparable wave of unrest in 2014.

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Violence has broken out across the country during almost daily anti-government protests in anger at President Nicolas Maduro's handling of a political crisis and a worsening economic situation that has caused severe shortages of food and medicine.

The protests erupted after the government-stacked Supreme Court issued a ruling March 29 nullifying the opposition-controlled National Assembly, a decision it later reversed amid a storm of domestic and international criticism.

The government is also setting up a controversial body called a constituent assembly, with authority to rewrite the constitution and shake up public powers.

Maduro says that is needed to bring peace to Venezuela, but opponents view it as a cynical tactic to buy time and create a biased body that could perpetuate the socialists' rule.

The opposition is demanding early elections, release of jailed activists and foreign aid to offset the economic crisis that has seen an unprecedented shortage of food and medicines.

The president accuses protesters of seeking a violent coup, and says he is the victim of an international right-wing conspiracy that has already brought down leftist governments in Latin America in recent years.

The government and the opposition have blamed each other of sending armed groups to sow violence in the protests, and deaths have occured on both sides.

'My world was falling in'

In Tachira, some 20 shops, restaurants and a school were looted on Wednesday, according to authorities. Two police stations were also set on fire and a military outpost attacked with firebombs during the previous night.

Fernanda Carvalho, 53, told the AFP news agency virtually all the food was stolen from her bakery in San Cristobal.

"It felt like my world was falling in. There go years of work and investment," she said.

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In the capital, Caracas, doctors and nurses protested to denounce a crisis that has left hospitals desperately undersupplied.

"We don't want weapons! We want medicine!" they yelled.

Maduro fired Health Minister Antonieta Caporale last week after her ministry released figures showing infant deaths soared 30 percent last year.

The US meddling stimulates the action of violent groups in Venezuela Rafael Ramirez, Venezuela's UN ambassador

Meanwhile, the US warned at the United Nations that Venezuela's crisis was worsening and could escalate into a civil conflict.

"We're starting to see serious instability in Venezuela," the US ambassador to the UN, Nikki Haley, told reporters after a closed-door Security Council meeting on Wednesday.

She had earlier warned that Venezuela was "on the verge of humanitarian crisis".

But Rafael Ramirez, Venezuela's UN ambassador, accused the US of encouraging violent elements within his country seeking to topple Maduro's government.

"The US meddling stimulates the action of violent groups in Venezuela," he said, after showing photos of vandalism and violence he blamed on opposition groups.

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UN ambassadors from Bolivia and Uruguay joined Caracas in rebuffing US attempts to address the ongoing in Venezuela before the UN Security Council.

Brazil's Defence Minister Raul Jungmann told reporters on Wednesday his country was making contingency plans for a possible influx of Venezuelan migrants.