Iran has seized another foreign tanker in the Gulf, state media reports claim.
Iranian forces seized the Iraqi ship for "smuggling fuel for some Arab countries" and detained seven sailors, according to the reports.
Iraq's oil ministry has said it has no connection to the seized vessel and that it is working to gather information about it.
The incident comes amid heightened tensions after the US tightened sanctions on Iran's oil sector.
The sanctions were reimposed after Washington's unilateral withdrawal from a landmark 2015 nuclear deal.
If confirmed, the Iraqi tanker would be the third foreign vessel to have been seized by Iran in recent weeks.
On 13 July, the Iranian coastguard detained the Panama-flagged MT Riah. The Revolutionary Guards' Sepah News site said at the time that the ship was seized during naval patrols aimed at "discovering and confronting organised smuggling".
Also last month, Iran seized the British-flagged tanker the Stena Impero in the Strait of Hormuz, saying it had collided with a fishing vessel.
What do we know about the latest seizure?
Fars news agency reported that the operation to seize the ship was carried out last Wednesday near the Gulf island of Farsi.
The vessel was carrying about 700,000 litres (154,000 gallons) of fuel at the time, according to a Revolutionary Guard Corps commander quoted in state media.
The tanker was reported to have been taken to Bushehr Port in south-western Iran and its fuel handed over to the authorities.
Iranian reports say the tanker was Iraqi but the nationalities of the seven crew have not been disclosed.
In a statement carried by the Iraqi News Agency, Iraq's oil ministry said it had no connection with the ship.
"The ministry does not export diesel to the international market," it said, adding that authorities were seeking more information about who the vessel belonged to.
Two Iraqi port officials told Reuters news agency that initial information suggested that the "small ship" belonged to a private shipping company owned by an Iraqi trader.
BBC Arab affairs editor Sebastian Usher says that though the cargo is relatively small, the seizure will inevitably raise tensions further in the region.
What's the background to this?
Tensions have been high in the Gulf since the US tightened oil sanctions against Iran.
The US has blamed Iran for two separate attacks on oil tankers in the Gulf of Oman in May and June - an allegation Tehran has denied.
Iran also shot down a US surveillance drone over the Strait of Hormuz in disputed circumstances.
UK warships have meanwhile been shadowing British oil tankers in the area since Iran threatened to seize one in response to the impounding of an Iranian tanker off Gibraltar.
They were, however, unable to prevent the seizure of the Stena Impero.
The UK said the tanker impounded off Gibraltar was suspected of breaching EU sanctions against Syria. Iran denied it was heading there.