Venezuela's attorney general has launched an investigation into El Salvador's President Nayib Bukele for alleged mistreatment of Venezuelan migrants.

A Houston refugee was sent back to Venezuela after months in an El Salvador megaprison, raising concerns over due process and political persecution.

Venezuela Attorney General Tarek Saab said on Monday that his office will investigate El Salvador's President Nayib Bukele and two other officials for the alleged abuse of Venezuelans who were detained in the Central American country.