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

The Venezuelans were deported in March under the 1798 Alien Enemies Act, which gives a US president power to detain and deport natives or citizens of "enemy" nations without usual processes. They were accused of belonging to a gang, something many of the men's relatives and lawyers deny.

Venezuela announced a probe Monday into torture claims by 252 migrants the United States had sent to a notorious Salvadoran prison where they said they were beaten, sexually abused and fed rotten food.