After retiring, Eusebio was an assistant coach for Benfica and travelled as a soccer ambassador.
The country's Football Federation and his former club Benfica also responded to his death and referred to him as an "eternal symbol".
"Portugal is mourning. Eusebio, the King of Portugal's 1966 team and the eternal symbol of the country, national team and Benfica passed away," the statement read.
Eusebio's body was taken to the Luz stadium later Sunday for fans to pay their last tributes. His body will remain at the stadium until Monday, according to local sports daily A Bola.
Prime Minister Pedro Passos Coelho recalled Eusebio in a statement as a "football genius, an excellent athlete and a generous and solidary," adding, he was "an example of professionalism and determination".
FIFA President Blatter said: "Football has lost a legend."
