The US military has flown an increased number of reconnaissance flights in international airspace off the coast of Venezuela during the last several days to gather classified intelligence about the embattled government of President Nicholas Maduro, according to two US defense officials.

The officials would not detail which US military aircraft are being used, but the Navy and Air Force maintain several large fixed-wing aircraft capable of intercepting communications and monitoring the status of weaponry.

The officials noted that the effort is limited to whatever the aircraft can gather by staying in international airspace.

Several US military officials continue to emphasize there are no military options actively being considered for the Venezuela crisis. For now, the US military would only contemplate a response if US assets, personnel or the embassy were attacked.

Venezuela is in crisis as self-proclaimed interim president Juan Guaido battles Maduro for control.

Guaido has called for other nations to send aid to the country in response to worsening food and medicine shortages. Maduro denies a humanitarian crisis exists in Venezuela and says the aid efforts are part of a coup attempt.

Over the weekend, violence broke out when the Venezuelan military blocked aid convoys at the country’s border.

In the state of Tachira, along the border with Colombia, more than 300 people were hurt in clashes that involved firearms and Molotov cocktails, said the Venezuelan government’s special envoy for Tachira state, Freddy Bernal.

He said the attacks were conducted by irregular groups protesting Maduro’s government on the international bridges along the border between Venezuela and Colombia — the Simon Bolivar bridge in San Antonio and the Francisco de Paula Santander bridge in Ureña.

“We registered no deaths despite the violent attacks for more than 15 hours of battle” by groups on the international bridges fighting “against thousands of patriots who fought and defended themselves,” he said. CNN has not independently verified the numbers of the injured in these clashes.

The opposition group said five people were killed. CNN has not verified those numbers.

In other developments:

• 274 service personnel from different branches of the Venezuelan armed forces have defected to Colombia, Migración Colombia, Colombia’s immigration agency, said in a statement Monday evening. Members of the national police, national guard, army and navy are among the defections, the statement said.

• The US Treasury Department imposed new sanctions against four Venezuelan governorsaligned with Maduro, effectively freezing their assets in the United States. The sanctions were imposed on these governors: Omar Prieto of Zulia, Rafael Lacava of Carabobo, Ramon Carrizalez of Apure and Jorge Garcia Carneiro of Vargas.

• More than 150 Venezuelan security forces have defected to Colombia in the last 48 hours, according to Colombia’s customs agency, Migration Colombia. Immigration officials said 146 Venezuelan forces entered through the department Norte de Santander and 10 entered through Arauca.

• The Brazilian president’s office said two trucks carring humanitarian aid that had crossed into Venezuelan territory from Brazil turned back around on Sunday. Citing “the impossibility of continuing into Venezuelan territory as planned,” the vehicles returned to the Pacaraima area of Brazil, a news release said.

• The US Federal Aviation Administration has issued a warning to US pilots about flying into and out of Venezuela because of “continued political instability and increasing tensions.”

• The United States requested that the UN Security Council to discuss Venezuela on Tuesday.

• UN Secretary General António Guterres has called for the end of violence in the Venezuelan conflict, his spokesperson, Stéphane Dujarric said Monday. “It’s very important for him that in no circumstances lethal force should be used against demonstrators,” Dujarric said.