CUCUTA, Colombia (AP) — The Latest on the political crisis in Venezuela (all times local):

1 p.m.

Two trucks carrying humanitarian aid from Brazil are stuck at the Venezuela border, contradicting earlier reports by opposition leaders that they had managed to break through a police blockade and enter the country.

An Associated Press journalist at the border said the trucks remain stationed in the arid expanse separating the Brazilian city of Pacaraima from the Venezuela city of Santa Elena de Uairen.

Earlier Juan Guaido on Twitter celebrated the arrival of what he said was the first truck of humanitarian aid, echoing comments from opposition lawmakers in Caracas who are monitoring the relief effort.

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12:55 p.m.

An army major says he's rejecting President Nicolas Maduro and throwing his loyalty behind the opposition's effort to bring aid into Venezuela.

Maj. Hugo Parra Martinez was the fifth member of the armed forces to abandon Maduro's socialist government on Saturday. A lieutenant and three sergeants of the National Guard surrendered earlier to officials in Colombia with raised hands.

Opposition leader Juan Guaido says the military is key to restoring democracy in Venezuela, although masses of soldiers appear to remain loyal to Maduro.

Images of Parra Martinez on social media and local broadcasters show him speaking through a megaphone that he's ready to join the struggle for Venezuela's freedom.

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12:20 p.m.

Thousands are flooding the streets of Venezuela's capital in rival demonstrations as opposition leaders vow to move shipments of humanitarian aid into the country despite objections from President Nicolas Maduro.

In Caracas, Maduro loyalists marched by the thousands to the city center to the sounds of brass bands, while others rode motorcycles.

Opposition supporters are converging on a Caracas military base, urging soldiers to join their fight. Many were dressed in the colors of Venezuela's flag and some came in costume as Capt. America characters.

Opposition leader Juan Guaido said emergency food and medicine would be delivered to Venezuela from three neighboring countries.

Maduro has closed Venezuela's borders and calls the aid part of a U.S.-led coup.

The opposition gathering in the capital was much smaller than that held by government supporters, but many Venezuelans who want Maduro to step down turned out en masse near the country's border crossings.

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11:40 a.m.

Opposition leader Juan Guaido says the first shipment of humanitarian aid has crossed into Venezuela from Brazil.

Guaido announced the crossing on his Twitter account Saturday. He called it a "great achievement."

The AP could not independently confirm the aid had passed through.

Guaido one month ago declared presidential powers, vowing to end what he calls the tyranny of President Nicolas Maduro.

A defiant Maduro denies a humanitarian crisis exists and has ordered the closing of Venezuela's borders to block Guaido's effort, which he says is part of a U.S.-led coup.

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11 a.m.

Opposition leader Juan Guaido has sent off a humanitarian aid convoy of trucks from Colombia toward the border of Venezuela at a pivotal moment in a showdown with President Nicolas Maduro.

Guaido on Saturday spoke from the border town of Cucuta, Colombia where U.S. aid has been stored.

Guaido says that he's standing among tons of supplies, but Maduro's government favors blocking it from entering peacefully into Venezuela, where it could save lives.

Maduro has closed the country's borders and National Guard soldiers have clashed with protesters.

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10:30 a.m.

Protesters along Venezuela's border with Colombia have stolen a red city bus and set it on fire to express outrage over thwarted humanitarian aid deliveries.

Flames from the bus blaze in the border town of Urena also caused nearby power lines to spark.

Protests broke out early in the day as opposition leader Juan Guaido vowed to move in emergency food and medicine from the United States over objections from President Nicolas Maduro.

But Guaido and other opposition leaders showed no immediate signs of being able to get the aid from a warehouse in Cucuta, Colombia to Venezuela.

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10:15 a.m.

The first truck with humanitarian aid from the Brazilian government has arrived in the city of Pacaraima on the border with Venezuela.

The crossing has been closed on orders from Venezuelan President Nicolas Maduro and the truck loaded with food and medicine will now wait in Brazilian territory.

Brazil's Foreign Minister Ernesto Araujo said he expects Maduro's government to allow the aid to pass.

"It is very exciting to see people anxious to recover their freedom and have a decent life," Araujo said.

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8:50 a.m.

Amid flaring tensions on the border, three members of Venezuela's National Guard have deserted their posts and solicited help from Colombia.

Colombian migration authorities said they received the request early Saturday at the Simon Bolivar bridge connecting the two countries.

There was no immediate word on the guardsmen's rank. But a video provided by Colombian authorities show the men wading through a crowd with their assault rifles and pistols held above their heads in a sign of surrender.

The young soldiers were then ordered to lay face down on the ground as migration officials urge onlookers to keep a safe distance.

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8:40 a.m.

Venezuela's National Guard has fired tear gas on residents clearing a barricaded border bridge between Venezuela and Colombia to let humanitarian aid pass through.

The tensions flared at dawn Saturday at the blocked entrance of the Francisco de Paula Santander bridge on the Venezuelan border town of Urena. 

Opposition leader Juan Guaido has vowed to bring humanitarian aid across into Venezuela from Colombia over objections from President Nicolas Maduro.

Venezuelan officials have ordered the border with Colombia closed after already shutting down crossings from Brazil and the island of Curacao, other points of entry for the aid.

But the residents in Urena have defied government orders and began removing yellow metal barricades and barbed wire.

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8:10 a.m.

Hundreds of Venezuelans have camped out overnight near a bridge in Colombia where humanitarian aid that the opposition will try to deliver inside the country is being stored.

Oriana Gutierrez says she traveled 14 hours to attend Friday's concert organized by billionaire Richard Branson and wanted to stay through the following day to help bring in aid.

Early Saturday some Venezuelans were singing their national anthem while others held hands in a prayer circle and asked God to protect their country.

President Nicolas Maduro has refused to accept the food and medical supplies donated largely by the United States, saying it's part of a larger plot to unseat him from power.

The opposition is planning to push in the aid using trucks and masses of people along border bridges connecting Colombia to Venezuela.

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6 a.m.

Venezuelans frustrated over their nation's crippling food and medical shortages are expected to join opposition leaders Saturday in a potentially risky push to deliver international aid that Nicolas Maduro has refused to accept into the country.

The opposition is calling on masses of Venezuelans to help trucks carrying the nearly 200 metric tons of humanitarian assistance delivered largely by the United States over the last two weeks across several border bridges in Colombia.

Once the trucks reach the border they'll face a crucial test: Whether the military standing guard on the other side will let them through.

Before daybreak Saturday, many national guards in riot gear forced people to move away from the road to the Simon Bolivar bridge connecting Venezuela and Colombia. The Venezuelan government had said that it was closing three of its bridges on the border.