Undocumented Colombian immigrants in Venezuela were packing up their belongings and crossing into their homeland on Tuesday after Caracas intensified a crackdown along the border between the two South American nations.

Many of the migrants are longtime residents of Venezuela who never gained legal status in the country, the Associated Press reported. They were abandoning their cinder block homes in a riverside shantytown after security forces told them to leave within 72 hours.

The government of embattled Venezuelan President Nicolás Maduro last week embarked on an aggressive "special operation" in Táchira state after two soldiers looking for smugglers had been attacked along its western border. Caracas temporarily shut down major crossings and deported hundreds of undocumented Colombians living in Venezuela.

Colombian Foreign Minister María Ángela Holguín and Government Ombudsman Jorge Armando Otálora on Monday assessed the situation in the border town of Cúcuta, the Spanish news agency EFE noted. And President Juan Manuel Santos warned on Wednesday that "prudence and diplomacy" must prevail in the tensions between the two neighbors.

"We demand that the government of Venezuela show respect toward all Colombians - those who are closely allied with our government, and also those who harshly criticize it " Santos said, according to El Heraldo.

Venezuelan Foreign Minister Delcy Rodríguez traveled to the Colombian city of Cartagena, where she urged the neighboring nation to "respect Venezuela's rights in the construction of a productive border, of peace and respectfulness of human rights," the semi-official Telesur television network reported.

Maduro, meanwhile, vowed to extend a crackdown on undocumented immigrants "in order to defend in the area from actions of paramilitary groups linked to (former Colombian President Álvaro) Uribe," Telesur noted. When he announced the border closures and special operation in the state, the president had urged citizens last week to "show solidarity with the armed forces."

"The military personnel who are at the border to defend the homeland," he said. "Enough of paramilitary terrorism! It's time for justice for Táchira."