A US judge has issued a scathing opinion against the Trump administration after immigration officials admitted to having mistakenly deported a man living in the US to a prison in El Salvador.

The opinion issued by US District Judge Paula Xinis on Sunday reaffirms her earlier ruling that demands Kilmar Abrego Garcia be returned to the US by Monday night.

The judge says Mr Garcia was seized "without any lawful authority" and held "without legal basis", in "direct contravention" of US law. She calls his situation a "grievous error" that "shocks the conscience".

Trump officials argue that they are unable to return him because they lack the authority to remove him from jail in El Salvador.