Local media claimed that the vessel, detained over alleged fuel smuggling, belonged to Iraq.
The Iraqi Oil Ministry has denied the ownership of the oil tanker, Reuters reported Sunday, citing local media.
"The ministry does not export diesel to the international market", the ministry said in a statement, cited by the Iraqi News Agency, according to Reuters.
The tanker was detained on Wednesday, according to the IRGC. The detained vessel is said to be transporting 700,000 liters (over 4,400 barrels) of fuel to "some Arab states". The tanker is now held in the Iranian port city of Bushehr. There were seven foreign citizens on board the ship, the IRGC said, adding that all had been detained.
Tensions in the Gulf region have been on the rise over the past several months. In July, the IRGC seized the UK-flagged Stena Impero oil tanker in the Strait of Hormuz over an alleged breach of international maritime regulations. An apparent tit-for-tat move, the boarding came two weeks after Iran's Grace 1 oil tanker was seized by the security forces from the state of Gibraltar and UK marines over an alleged breach of the EU's anti-Syria sanctions.
Several other oil tankers have been attacked in the Strain of Hormuz since May. The United States and its allies blamed Iran for the incidents, while Tehran has denied being involved.