Embattled Venezuelan President Nicolás Maduro claimed on Monday that his Colombian counterpart, Juan Manuel Santos, had sanctioned a plan to assassinate him.

Maduro, who in the past has leveled similar allegations against leaders ranging from U.S. President Barack Obama to Caracas Mayor Antonio Ledezma, failed to provide any evidence to substantiate his allegations, the Associated Press reported.

His remarks come in the midst of a border crisis with neighboring Colombia, which his government has used to declare a state of emergency, close key border checkpoints, and deport more than 1,000 undocumented Colombian immigrants. During a state visit to Vietnam, Maduro promised that he would soon provide additional details on the supposed plot, El Universal detailed.

"From Bogotá, they are attacking us now," the socialist leader exclaimed. "I have proof, which I will show you, that shows how a campaign is being carried out to kill me -- with the consent of the government of Colombia, which is turning a blind eye, unfortunately -- to kill President Nicolás Maduro."

The Venezuelan president further accused Santos of having lost his mind, the newspaper noted. His counterpart was "letting himself being led by his advisers," Maduro added.

However, President Santos has advocated for continued dialogue, claiming that diplomacy must be the way for the two nations to reconcile. 

With Maduro in Asia, diplomats from 34 Western Hemisphere nations were meeting at the Organization of American States (OAS) in Washington to discuss the South American nations' border crisis at an emergency meeting, the AP noted. Colombia failed to reach the needed 18 votes to compel a meeting of the bloc's foreign ministers, but South American envoys are set to discuss the crisis at a summit in Quito, Ecuador on Thursday.

Nonetheless, Foreign Affairs Minister Mária Angela Holguín lamented the organization's decision. 

"The continent is the one that has lost, the OAS has lost the chance to have an important debate on human rights, on the rights of immigrants," she stated in a press release.

The Venezuelan military, meanwhile, on Monday bolstered its presence in western Táchira state and started taking a census in towns along the border with Colombia, Agence France-Presse reported. The survey will take a tally of people, homes, commercial and industrial properties, public services, and economic and farming activity, and may be linked to Maduro's efforts to expel suspected smugglers from the area.

Since the state of emergency was declared last week, Venezuelan authorities said they have also closed 177 illegal border crossings, AFP added.