The Nigerian navy said on Tuesday that it had arrested 22 Chinese nationals for fishing in its territorial waters without permits and travel passports.

Four foreign vessels and their crew were held in the operation, Commodore Godwin Ochai told reporters in Onne, outside the southern oil city of Port Harcourt.

"When our troops went on board... they discovered that the four vessels had no immigration documents, neither did its 22 crew members have international passports," he added.

"We discovered that the suspects did not have any form of permit to engage in fishing activities in the nation's territorial waters."

The suspects, who were arrested last Friday, were later handed over to Nigeria's immigration service for further investigation, Ochai said.

The impounded vessels were carrying several tons of fish. Television footage showed images of the Chinese nationals being paraded before reporters.

Ochai alleged that the Chinese had breached international maritime laws and procedure by fishing in Nigerian waters without authorisation.

"The Nigerian navy... will continue to go after both foreign and domestic threats capable of undermining the nation's security and economy," he said.

"We will go after them, arrest them and put them forward for prosecution."

A Nigerian immigration officer, Briggs Dawaye, said that a thorough probe would be conducted.