A truck loaded with humanitarian aid was set ablaze on Saturday on the Colombia-Venezuela border, an opposition deputy told reporters amid rioting on the Santander bridge crossing.

Deadly clashes have erupted in border towns across Venezuela as opposition activists try to bring aid into the country across government blockades.

Troops fired tear gas at people looking to cross into Colombia and at least 13 members of the security forces have abandoned their posts.

"People are saving the bulk of what's on the first truck, and looking after the humanitarian aid that Maduro, the dictator, ordered burned," the deputy, Gaby Arellano, said.

Venezuelan soldiers had earlier halted the passage of four aid trucks at the bridge and fired tear gas at demonstrators accompanying the trucks.

President Nicolas Maduro announced Saturday he was severing diplomatic ties with Venezuela's neighbor Colombia after it backed his rival Juan Guaido in his attempts to bring humanitarian aid into the country.

"I have decided to break off all political and diplomatic relations with the fascist government of Colombia," Maduro told a huge rally of his supporters in the capital Caracas.

He gave Colombia's diplomats 24 hours to leave the country. "Get out of here, oligarchs!" he said.

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