Mexico has accused Bolivia of intimidating its diplomats in La Paz after a chill in relations since Mexican President Andres Manuel Lopez Obrador last month gave political asylum to former Bolivian president Evo Morales.
Mexico says Bolivian security forces have increased their presence around the Mexican ambassador's La Paz residence, where a group of former Cabinet ministers and others loyal to ousted president Evo Morales have sought refuge.
Troops gathered in larger numbers around the residence on Tuesday, the Mexican Foreign Ministry said. Maximiliano Reyes, Mexico's undersecretary for Latin America, described the Bolivian patrols around the diplomatic property as a "siege."
Relations between the two countries have been strained since Mexico granted asylum to Morales after he resigned November 10 following national upheaval over his claim of victory in an election marred by vote-rigging. Morales has since relocated to Argentina and says he plans to stay involved in politics in neighboring Bolivia, while some former top aides remain holed up in the Mexican ambassador's residence.
Willson Santamaria, Bolivia's deputy minister of public security, said the Morales loyalists would not be allowed to leave the country.
"We have taken the necessary steps so that the security forces immediately track and detect any help, any complicity in helping the fugitives flee the country," he said.
Those who sought refuge in the Mexican ambassador's residence include Juan Ramon Quintana, the former chief of staff for Morales, and five other former ministers, according to a Mexican federal official. The official was not authorised to comment publicly about the matter and spoke on condition of anonymity.
Several are accused by the interim government of President Jeanine Anez of electoral fraud or other crimes.
Mexico has complained that Bolivian security and intelligence officials have surrounded both the Mexican ambassador's residence and the embassy, recording the movement of people in and out of the facilities and even impeding the "free transit" of the ambassador.
Erick Foronda, Bolivia's presidential secretary, denied that authorities are interfering with the movements of Mexico's diplomats. The police presence at the diplomatic facilities was increased for security reasons following reports of planned demonstrations in the area, he said.