By Nelson Bocanegra and Anggy Polanco
CUCUTA, Colombia/URENA, Venezuela, Feb 23 (Reuters) - V enezuelan troops fired tear gas at angry protesters unable to cross into Colombia on Saturday after President Nicolas Maduro closed the border to stop the opposition bringing U.S. humanitarian aid into the South American nation.
Demonstrators set up barricades and burned tires in the Venezuelan border town of Urena, as attention turned to whether National Guard troops stationed at the border crossing would fulfill Maduro's orders to block humanitarian aid from reaching a sick and hungry population.
Four National Guard troops at the frontier disavowed Maduro's socialist government on Saturday, following an appeal from Venezuelan opposition leader Juan Guaido to let aid through.
A social media video showed the troops driving armored vehicles across a bridge linking the two countries, knocking over metal barricades in the process, and then jumping out of the vehicles and running to the Colombian side.
"Among the troops, whether they are in the army, air force, navy or National Guard, many people disagree (with what is happening)," one of the troops, an officer whose uniform carried the name Linarez, told reporters after entering Colombia, according to another video on social media. "You can't say anything against the government. It's treason."
Colombia's migration authority confirmed the defection of the four Venezuelan soldiers.
Leaders of Venezuela's ruling Socialist Party call the aid effort a veiled invasion backed by Washington, and insist that the United States should instead help Venezuela by lifting crippling financial and oil sector sanctions.
Venezuela's opposition says that while the need for basic food and medicines is desperate, the aid operation is also meant to embarrass military officers who continue to support Maduro's increasingly isolated government.
Demonstrators in Urena who blocked roads and burned tires also threw rocks at security forces who responded with volleys of tear gas.
The troops had earlier blocked people from crossing the border into Cucuta, where many Venezuelans now work, shop or send their children to school amid Venezuela's continued economic collapse.
"We were all going to work. We want to work: the people attempted to force their way through," said Viviana Meza, 29, who works in a Cucuta restaurant.
Guaido, recognized by most Western nations as Venezuela's legitimate head of state, defied court orders not to leave the country when he traveled on Friday to Cucuta, where aid from the U.S. and Colombian governments is stockpiled in warehouses.
Guaido was due to hold a news conference with the presidents of Colombia, Chile and Paraguay in Cucuta on Saturday morning before escorting the aid toward the border on foot.
A line of heavy trucks packed with aid supplies waited to attempt the crossing, in front of rows of television cameras.
CONCERNS ABOUT VIOLENCE
U.S. President Donald Trump's national security adviser John Bolton canceled plans to travel to South Korea to prepare for a summit addressing North Korea's nuclear program in order to focus instead on events unfolding in Venezuela, his spokesman said on Friday.
"To Maduro's military cronies attacking civilians at the Brazilian border - the world is watching and the perpetrators will face justice," Bolton wrote on Twitter. "The Venezuelan military should protect civilians, not shoot them.
Guaido, 35, head of the opposition-run Congress, has provided few details on the transport plan. Trucks are expected to be driven by Venezuelan volunteers and some opposition figures have suggested forming human chains.
Maduro blames the country's dire situation on U.S. sanctions that have blocked the country from obtaining financing and have hobbled the OPEC nation's oil industry.
Concerns about the potential for violence flared on Friday when the Venezuelan army opened fire in an village near the Brazilian border after indigenous leaders attempted to prevent them from advancing, killing a woman and her husband.
The U.S. government condemned the killings.
The U.S. envoy for Venezuela, Elliott Abrams, who traveled to Cucuta on Friday, called them "a crime and a disgrace", while the U.S. State Department said "egregious violation of human rights by Maduro and those who are following his orders will not go unpunished."
Venezuelan troops on Saturday morning had blocked the Brazilian border despite protests by villagers in the nearby town of Santa Elena de Uairen who burned a bus, a truck and a National Guard office overnight.
"The situation is critical and we should be all united to allow the aid to pass," said shopkeeper Jeremy Ortega, 21.
Brazil sent two small trucks with food and medicine to the border on Saturday, after the border closure foiled its plan to have more Venezuelans drive vehicles to pick up the 200 tonnes of aid it has stockpiled in the northern city of Boa Vista.
Brazilian Foreign Minister Ernesto Araujo urged Venezuela's military to let the trucks in.
Nearly 200,000 people attended a benefit concert in Cucuta on Friday featuring Latin pop stars, including Luis Fonsi of "Despacito" fame, many of whom called on Maduro to step down.
A rival concert held by the ruling Socialist Party on the Venezuelan side was sparsely attended.
Guaido in January invoked articles of the constitution to assume interim presidency and denounced Maduro as a usurper, arguing his 2018 re-election was illegitimate. (Writing by Brian Ellsworth; Additional reporting by Helen Murphy and Julia Symmes Cobb in Bogota, Anthony Boadle in Brasilia; Editing by Daniel Flynn and Daniel Wallis)
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