The ministry said the boat, a tug owned by a Naples-based firm, had three Italian citizens aboard, and another man whose citizenship is unknown, when the crew was abducted Sunday.
The Nigerian navy said a search for the crew members began immediately.
The International Maritime Bureau reported the pirates were armed and there were no injuries to the crew during the abduction, adding the vessel continued undamaged to port.
Hijackings in Nigerian waters are common, the Italian news agency ANSA reported Monday, and are generally conducted to seize cargo, unlike hijackings for ransom in Somali waters.
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