At least four civilians were killed Saturday as Venezuelan security forces clashed with demonstrators at the border with Brazil over deliveries of humanitarian aid.

“Today’s events force me to make a decision to formally propose to the international community that we must have all options open to secure the freedom our country,” Venezuelan opposition leader and interim-president Juan Guaido wrote on Twitter late Saturday.

Also late Saturday, U.S. Vice President Mike Pence announced plans to meet with Guaido Monday in Bogota. Pence is scheduled to address the Lima Group of regional leaders in Colombia Monday and will meet with Guaido while he is there.

Pence could announce new sanctions at the Lima Group meeting, adding to sanctions on PDVSA, the state-owned oil company.

Foro Penal [Criminal Forum], a group that tracks violence in Venezuela, reported the four deaths Saturday. It said they took place in Santa Elena de Uairen near the border with Brazil. It said the victims were shot by pro-government militia members.

A spokesman for the group, Alfred Romero, posted a video on Twitter saying more than two dozen other people were wounded in the violence.

The Colombian migration authority provided photos The Colombian migration authority provided photos Feb. 23, 2019, of some of the 23 Venezuelan uniformed personnel, including 20 soldiers, who crossed into Colombia and surrendered. The Colombian migration authority provided photos Feb. 23, 2019, of some of the 23 Venezuelan uniformed personnel, including 20 soldiers, who crossed into Colombia and surrendered.

At one border point, aid trucks caught fire, leading the crowd to rush to save the boxes of food and medical supplies.

Late Saturday U.S. Senator Marco Rubio tweeted that a Venezuelan lawmaker and his assistant had been poisoned. The assistant is dead, according to Rubio’s post and the lawmaker is in “serious condition.”

Grave situation developing right now inside of #Colombia.@freddysuperlano a member of the National Assembly of #Venezuela was poisoned this morning at breakfast inside of Colombia & is in serious condition at the hospital.His assistant Carlos Salinas has died from poisoning. — Marco Rubio (@marcorubio) February 24, 2019

Soldiers surrender

Colombian officials say more than 60 Venezuelan soldiers defected Saturday.

Venezuelan Army Major Hugo Parra announced his defection Saturday, telling VOA Noticias he recognizes opposition leader Juan Guaido as the legitimate president of Venezuela.

Guaido tweeted his praise of the soldiers’ actions.

“They aren’t deserters,” he said. “They’ve decided to put themselves on the side of the people and the constitution.”

Venezuela's opposition leader Juan Guaido speaks f Venezuela's opposition leader Juan Guaido speaks flanked by Chile's President Sebastian Pinera, left, and Colombia's President Ivan Duque in front of a warehouse housing U.S. humanitarian aid destined for Venezuela, in Cucuta, Colombia, Feb. 22, 2019. Venezuela's opposition leader Juan Guaido speaks flanked by Chile's President Sebastian Pinera, left, and Colombia's President Ivan Duque in front of a warehouse housing U.S. humanitarian aid destined for Venezuela, in Cucuta, Colombia, Feb. 22, 2019.

?Cutting Colombia ties

Disputed President Nicolas Maduro announced in a speech to his supporters Saturday that he is cutting off diplomatic ties with Colombia. Colombia President Ivan Duque has been making public appearances Saturday with Guaido as they work to transport aid across Venezuelan borders.

Duque said Colombian ambassadors and consuls have 24 hours to leave Venezuela.

Colombian Foreign Minister Carlos Holms Trujillo released a statement in response, saying, “Colombia holds the usurper Maduro responsible for any aggression or violation of the rights of Colombian officials in Venezuela.”

Maduro also said he would defend Venezuela’s independence with his life. He called Guaido a puppet of the White House.

He said if the United States attacks his country, “they will be received by the strength of the Venezuelan armed forces.”

Meanwhile, U.S. President Donald Trump tweeted his support for Guaido.

The people of Venezuela stand at the threshold of history, ready to reclaim their country – and their future.... pic.twitter.com/ajxd1EN64c — Donald J. Trump (@realDonaldTrump) February 23, 2019

God Bless the people of Venezuela! — Donald J. Trump (@realDonaldTrump) February 23, 2019

?Aid shipments

Earlier Saturday, Guaido used Twitter to hail the first shipment of humanitarian aid arriving in Venezuela from its southern neighbor Brazil.

“This is a great achievement, Venezuela!” Guaido said in a tweet Saturday.

However, there were mixed reports about whether the aid actually made it to its destination, or remained stalled at the border.

A U.S. State Department official traveling with the aid convoy told VOA the shipment contained about 200 tons of food and medicine from the U.S. and Brazilian governments. They had been stored at a military base in Bao Vista, Brazil.

Demonstrators run away from a cloud of tear gas du Demonstrators run away from a cloud of tear gas during clashes with the Bolivar National Guard in Urena, Venezuela, near the border with Colombia, Feb. 23, 2019. Demonstrators run away from a cloud of tear gas during clashes with the Bolivar National Guard in Urena, Venezuela, near the border with Colombia, Feb. 23, 2019.

?Venezuelans clash with troops

In the town of Urena, clashes took place early Saturday between Venezuelan National Guard troops and residents who were clearing a bridge so aid trucks from Columbia could enter the country. The troops fired tear gas and buckshot at the residents, some of whom hurled rocks in return. A city bus was also set on fire.

Urena, Venezuela Urena, Venezuela Urena, Venezuela

Local health officials in Urena told the Associated Press that at least two dozen people were injured.

Rights group Amnesty International on Saturday called on Venezuela to stop attacking its citizens, saying such attacks constitute serious human rights violations.

FILE - Venezuela's President Nicolas Maduro attend FILE - Venezuela's President Nicolas Maduro attends a gathering in support of his government in Caracas, Venezuela, Feb. 7, 2019. FILE - Venezuela's President Nicolas Maduro attends a gathering in support of his government in Caracas, Venezuela, Feb. 7, 2019.

?Despite the nation’s rampant inflation and food shortages, embattled President Nicolas Maduro has rejected offers of aid from other countries, saying his countrymen are not beggars.

But Guaido, who has declared himself interim president, vowed to see that the donated supplies piled into warehouses at Venezuelan border crossings are allowed into the country. Throngs of people camped out overnight to help with the deliveries.

A Colombian police officer helps men who were hurt A Colombian police officer helps men who were hurt in clashes at the Simon Bolivar Bridge on the Colombia-Venezuela border near Cucuta. A Colombian police officer helps men who were hurt in clashes at the Simon Bolivar Bridge on the Colombia-Venezuela border near Cucuta.

?Civilians killed Friday

On Friday at the crossing at the Brazilian border, at least two civilians died in a clash with Venezuelan soldiers. Witnesses say the security forces used tear gas and bullets on demonstrators calling for the delivery of aid. The demonstrators reportedly fought back with arrows and rocks.

The White House said in a statement late Friday that the U.S. “strongly condemns the Venezuelan military’s use of force against unarmed civilians and innocent volunteers on Venezuela’s border with Brazil.”The statement also said: “Egregious violation of human rights by Maduro and those who are following his orders will not go unpunished.”

Reymar Perdomo sings "I Left," during the Venezuel Reymar Perdomo sings "I Left," during the Venezuela Aid Live concert on the Colombian side of the Tienditas International Bridge near Cucuta, Colombia, on the border with Venezuela, Feb. 22, 2019. Reymar Perdomo sings "I Left," during the Venezuela Aid Live concert on the Colombian side of the Tienditas International Bridge near Cucuta, Colombia, on the border with Venezuela, Feb. 22, 2019.

?Venezuela Live Aid

Also Friday, Guaido defied a government ban to leave Venezuela and attended the “Venezuela Live Aid” concert, which was arranged by British billionaire Richard Branson in Colombia to raise funds for the relief campaign.

Guaido claimed at the concert he arrived in Colombia with the help of the Venezuelan military, whose most senior officers have repeatedly declared absolute loyalty to Maduro.

As head of the opposition-led National Assembly, Guaido invoked the constitution to declare himself interim president after saying Maduro’s reelection last year was a sham.

The U.S. was the first to recognize Guaido as president, followed by about 50 other nations.

Maduro has offered to meet with Guaido, but is refusing to step down or call for early elections.

The collapse in global energy prices, corruption and failed socialist policies have left oil-rich Venezuela’s economy in shambles.

More than 3 million people have fled the country’s political and economic crisis since 2015.

VOA Noticias contributed to this report.