CUCUTA, Colombia/URENA, Venezuela, Feb 23 (Reuters) - Venezuelan troops loyal to President Nicolas Maduro fired tear gas and rubber pellets at opposition supporters seeking to bring foreign aid over the Colombian border on Saturday, as the country’s socialist government defied international pressure to step down.

The clashes occurred as Venezuelan opposition leader Juan Guaido, who most Western nations recognize as Venezuela’s legitimate leader, gave a personal send off to an aid caravan from the Colombian city of Cucuta.

Guaido briefly boarded one of a dozen trucks carrying U.S.-backed humanitarian aid before they set off towards the border, where they were pushed back by Venezuelan security forces.

Colombia’s government said their contents would be unloaded and transported by “human chains” that have formed on the road that leads towardVenezuela.

But in the towns of San Antonio and Urena, just across the border, troops fired tear gas and rubber bullets at opposition activists including lawmakers walking towards the frontier who were waving Venezuelan flags and chanting “freedom.”

Witnesses reported constant gunfire without being able to identify the origin.

“They started shooting at close range as if we were criminals,” said shopkeeper Vladimir Gomez, 27, wearing a white shirt stained with blood. “I couldn’t avoid the (rubber) bullets and they hit me in the face and my back. We have to fight.”

Many of the demonstrators said they were peaceful civilians who simply wanted aid because of widespread food and medicine shortages in the once-prosperous country suffering an unprecedented economic meltdown.

“I’m a homemaker, and I’m here fighting for my family, for my children and parents, resisting the military’s tear gas and soldiers on motorbikes,” said Sobeida Monsalve, 42.

Others barricaded streets with burning tires, set a bus alight and hurled stones at security forces to demand that Maduro allow aid into a country ravaged by food and medicine shortages in the wake of an economic meltdown.

National guard troops also fired tear gas in Santa Elena near the Brazilian border where people tried set up barricades to prevent armed pro-government agitators from entering.

On Friday, troops had opened fire in a village in the area killing a woman and her husband. Thirty-five National Guard troops are being held by the indigenous community in protest, the mayor of the broader Gran Sabana municipality said.

Two humanitarian aid trucks crossed the Brazilian border although they had not passed through the Venezuelan customs checkpoint, according to a Reuters witness.

EMBARRASS THE MILITARY

A social media video showed troops who defected on Saturday driving armored vehicles across a bridge linking Venezuela and Colombia, knocking over metal barricades in the process, and then jumping out of the vehicles and running to the Colombian side.

“What we did today, we did for our families, for the Venezuelan people,” said one of the four men in a video televised by a Colombian news program, which did not identify them. “We are not terrorists.”

Colombian television also showed images of what it said was a Venezuelan officer who identified himself as Major Hugo Parra, recognizing Guaido as president.

Thirteen members of Venezuelan securities forces had defected on Saturday, including 10 members of the National Guard officers and two police officers, Colombia’s migration authority said.

Leaders of Venezuela’s ruling Socialist Party call Guaido’s 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. Maduro blames the country’s dire situation on U.S. sanctions that have blocked funds and hobbled the OPEC member’s oil industry.

Thousands of government supporters clad in signature red shirts led a rally in downtown Caracas to denounce intimidation by the United States and to demand that the Trump administration halt sanctions.

“The humanitarian aid they want to bring is a fraud, those products are no apt for human consumption,” said Maryori Romero, 56, who works at a state-run supermarket.

While the need for basic food and medicines is desperate, Venezuela’s opposition also hopes the operation will embarrass military officers who continue to support Maduro.

Thousands of white-clad protesters gathered at a military base in Caracas to demand that the armed forces allow the aid in, after declaring the aid on its way in a news conference flanked by three Latin American presidents, including Colombia’s Ivan Duque.

“This is the biggest battle that the armed forces can win,” said Sheyla Salas, 48, who works in advertising. “Please join this struggle, get on the right side (of history), allow the humanitarian aid to enter.”

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.

(Writing by Brian Ellsworth; Additional reporting by Helen Murphy and Julia Symmes Cobb in Bogota, Anthony Boadle in Brasilia; Ricardo Moraes in Pacaraima, Angus Berwick in Caracas, Editing by Daniel Flynn, Daniel Wallis and Grant McCool)