In a statement, Iraq's Oil Ministry said the ship seized in the Persian Gulf is a small vessel which the ministry does not deal with in the process of oil marketing.
The authorities were trying to gather information about the ship seized by Iran, the statement added.
Earlier in the day, Iran had said the tanker seized by its Revolutionary Guards Corps (IRGC) on Wednesday was an Iraqi vessel, according to IRNA news agency.
The IRGC said in a statement that the oil tanker was attempting to smuggle 700,000 liters of oil to the Gulf countries and that seven foreign nationals aboard the vessel were detained.
Last month, Iran seized a British-flagged tanker in the strategic Strait of Hormuz, in a retaliatory action for the seizure of an Iranian vessel by Gibraltar -- a British overseas territory. Tension has been high in the region since then.
(Anadolu Agency)