The port authority said it would examine the bids in detail before choosing one by the end of the month.
Coming in second with a EUR4.4 billion bid was a joint venture of Hong Kong's Hutchison Port Holdings, Hutchison Ports Investments and Greece's Alapis Holding Industrial and Commercial and its subsidiary Lyd SA.
The Athens-listed Piraeus Port Authority (PPA), which runs the biggest port in Greece, has received bids more than EUR4 million, reported Lloyd's List. The PPA share price ended trading 14 per cent up. Both Cosco's and Hutchison's bid exceeded market estimates which ranged between EUR1-2 billion.
Cosco and the Hutchison consortium have also bid for control of container action at Greece's second-largest port Thessaloniki.