Portugal has declared three days of national mourning after one of its greatest footballers, Eusébio, died after reportedly suffering a heart attack at his home in Lisbon.

Eusébio, 71, who was born in Mozambique, played for Portugal, becoming the first black African global soccer star.

Portugal's president, Aníbal Cavaco Silva, addressed the nation on television to praise the "affability and humility" of a man who never let stardom go to his head despite being one of the game's most prolific goal scorers. "His talent brought joy for entire generations, even those who didn't live through the most glorious moments of his career," he said.

Eusébio emerged as football's popularity was exploding across the world and he was partly responsible for the globalisation of the sport. He was revered as highly as George Best, Franz Beckenbauer, Johan Cruyff, Bobby Moore and Pelé. "One of the greatest football players ever has passed away," Beckenbauer said.

Tributes poured in from around the world. The Portugal and Real Madrid star Cristiano Ronaldo tweeted: "Always eternal #Eusebio, rest in peace." Luís Figo, another Portuguese great, tweeted: "'The king!! Grande perda para todos nos! O mais grande!! [Great loss to all of us]."

Chelsea's Portuguese manager, José Mourinho, described him as immortal. "For us, for you Eusébio is one of the greatest footballers. For Portugal he means more than that. No colour, no clubs, no political sides. For Portuguese people Eusébio is Eusébio.

"I [have known] him since [I was] a kid. He played against my father. Every year when I was a kid he was sending me a shirt, a ball, a boot. I think guys like him, they never die. History doesn't let them die."

A striker, Eusébio was blessed with outstanding pace and skill and possessed a fearsome shot. According to Fifa records, he scored 679 goals in 678 official games.

During his 15 years at Benfica, the club reached four European Cup finals. It won once, in 1962 against Real Madrid, and the game is remembered for the two Eusébio goals that won the match. They lost the other three, the most famous of which was the 4-1 defeat to Manchester United at Wembley in 1968. Eusébio had a chance to win it for Benfica , but when his shot was saved by United's goalkeeper, Alex Stepney, Eusébio applauded because of his "sense of fair play". United won in extra time.

"He was certainly one of the game's greats," Stepney said. "To score that many goals is incredible. I don't care who you are, what era you play in, to do that is some achievement."

Eusébio was the son of Laurindo António da Silva Ferreira, a white Angolan, and Elisa Anissabeni, a black Mozambican. He was brought up in poverty, playing football on the streets with a ball of rags, but moved to Lisbon in 1961, joining Benfica and blazing a trail to Europe for African talent that was followed, by the likes of George Weah, Didier Drogba and Samuel Eto'o.

As Mozambique was a Portuguese colony at the time, Eusébio represented Portugal at international level and became a national hero with his wonderful performances at the 1966 World Cup in England. The team was beaten 2-1 in the semi-final by England, the eventual winners, and had to settle for third place. Eusébio won the Golden Boot with nine goals but never played in another World Cup.

His impact was huge in Portugal and Africa, and the Portuguese government decreed three days of national mourning, with flags flying at half-mast, while the Portuguese Football Federation ordered a minute's silence ahead of yesterday's Portuguese cup games.

After leaving Benfica, Eusebio was barred from a lucrative move to Italy by the intervention of the Portuguese dictator, António Salazar, and moved instead to the North American Soccer League. After retiring, he returned to Portugal, where he became an ambassador for Benfica and his adopted country. He reportedly suffered a cardiac arrest and is survived by his wife, Flora, two daughters and several grandchildren.