Mwangura said the Centauri was now being taken towards Eyl, a lawless former fishing outpost on the Somali coast where gangs are holding several ships for ransom.
"The ship was expected to call at Mombasa (Kenya) on September 19 and discharge 17,000 tonnes of bulk salt," he said. "It was taken in southern Somalia, which is unusual for the pirates."
The Great Creation was travelling to India from Tunisia with 24 Chinese and a Sri Lankan on board when it was attacked.
There were no immediate details on the Greek ship's crew.
Somali pirates are holding 13 vessels captive at the moment, along with more than 200 sailors. Most of the gangs are based in northern Somalia's Puntland region, where security forces reportedly clashed with pirates on Thursday.
Local media said several pirates had been injured and others arrested during the gunfight on the outskirts of Bosasso port.
Spain said on Wednesday that a military aircraft would patrol the waters off Somalia to guard against the gunmen.
The plane will observe the pirates' movements and relay information to a European Union task force formed to tackle piracy.
Meanwhile, shipowners on Thursday urged the United Nations to commit more warships to patrol the commercially strategic Gulf of Aden to counter the rising levels of piracy.
"The shipping industry's plea is in response to a situation which it describes as in danger of spiralling completely and irretrievably out of control," the bodies, which include leading ship associations and transport unions, said.
The sea lane in the Arabian sea between Yemen and Somalia links the Gulf and Asia to Europe and beyond via the Suez Canal and is critical to Gulf oil shipments.
The groups said nearly 40 hijackings had taken place in the Gulf of Aden alone this year with 133 kidnapped crew and ten ships being held.
The London-based International maritime bureau estimates that over 1,200 Somalis and at least six major gangs are involved in the attacks.