Colombia’s outgoing leftist president, Gustavo Petro, said Monday he has evidence of fraud in the presidential election and warned that the far-right president-elect’s rise to power could lead to “civil war.”

Abelardo de la Espriella, 48, will be sworn in on Friday in a ceremony in the southwestern city of Cali, contrary to the tradition of holding the inauguration in Bogota before Congress.

“We are facing fraud and an undoubtedly profound institutional problem, namely the inauguration of an illegitimate president,” Petro said Monday at a press conference.

Petro said June’s runoff election involved “algorithmic, systemic electoral fraud on an enormous volume of votes,” allegedly orchestrated from abroad against his ally, Ivan Cepeda.

“Foreign money and foreign companies with the capacity to manipulate algorithms” interfered in the outcome of the electoral process, Petro said.