Kyriakou suffered a heart attack on Sunday (July 2), the private Athens Medical Centre said.

The Greek shipping and media mogul became head of the HOC shortly after Athens had hosted the 2004 Olympic Games.

He served in the position until 2009 when he lost a bitter election against Spyros Capralos, who remains President of the HOC today.

Kyriakou was also President of the Hellenic Athletics Federation (SEGAS) and a former member of the International Association of Athletics Federations (IAAF) ruling Council.

He was elected to the IAAF Council in 2003.

Kryiakou was also President of the International Olympic Academy from 2004 until 2009. 

As President of SEGAS, he found himself at the centre of worldwide controversy in 2004 when he threatened to defy the International Olympic Committee (IOC) and let sprinters Kostas Kenteris and Katerina Thanou compete, despite their refusals to provide drug test samples. 

A year later, when Kyriakou successfully stood for the Presidency of the HOC, the IOC was forced to send an official observer to the meeting after receiving complaints over the handling of the election.

At one time, Kryiakou had announced plans to stand for President of the IAAF against Lamine Diack but his challenge was stifled. 

He left the IAAF Council in 2007. 

Away from sport, Kryiakou was one of Greece's best-known businessmen and a billionaire.

At the age of 23, Kyriakou started his own shipping company, Athenian Tankers, and remained involved in the sector until his death. 

He was the chairman of media conglomerate Antenna Group, which he founded in 1989. 

It includes radio and television stations in Greece and several Balkan countries, internet providers and a publishing house.

Kyrakou also reportedly owned the world's largest private collection of Nazi memorabilia,

"It is with deep emotion and sadness that the Kyriakou family bids farewell to our beloved Minos, who left life suddenly from a heart attack in the late afternoon," a spokesman for ANT1, Greece's flagship commercial channel, said.

"Respect and deep sorrow are upon all the people who work in all the businesses of Minos Kyriakou’s Group."

The HOC announced that flags at its headquarters would be hung at half-mast to mark Kyrakou's death. 

Twice divorced, Kyriakou is survived by two sons and a daughter from his first marriage.