Atletico Madrid midfielder Paulo Assuncao has revealed he quit Porto amid threats from the club's ultras.

Assuncao says after one Porto training session, he was approached by four fans, who warned him that "if I soon did not extend my contract, I would be shot in the knee.

"I replied that I didn't believe them, but I was scared for my life."

Assuncao also revealed he was followed by the same ultras in a car and had to ask for security from the club to protect his wife and family.