Iran has seized another foreign tanker in the Gulf, according to the country's state media.
Tehran claimed the tanker had been smuggling fuel for Arab countries.
The media has quoted a Revolutionary Guard commander as saying the tanker was carrying 700 thousand litres of fuel and that seven crew had been detained.
The local reports did not provide further details about the vessel or the nationality of the crew.
State media also reported that Iranian forces seized a ship in the Gulf which they suspected of carrying smuggled fuel.
It marks the Revolutionary Guard's third seizure of a vessel in recent weeks and the latest show of strength by the paramilitary force amidst an increase in regional tensions.
Guard commander General Ramazan Zirahi was quoted by Iran's state TV saying the ship was seized in Iranian territorial waters and had been transporting diesel fuel.
State television and other local media also ran footage of the ship but did not show any flag or identifying marker for the vessel.
In an interview on state media, General Ramazan Zirahi said: "A foreign vessel was seized in the Islamic Republic's territorial waters, while it was carrying out professional and organised fuel smuggling with seven crew members."
General Zirahi claimed it was carrying 700,000 litres of "smuggled diesel fuel and currently both the vessel and its crew members have been detained and are undergoing legal procedures".
Adnan Tabatabi, Iran expert and founder of Middle Eastern affairs thinktank Carpo, told Euronews' Good Morning Europe show that Iran feels compelled to show that it can "stop tankers if it feels like it".
He continued: "I believe that the strategy here is to show what the costs of the US sanctions strategy are and that trying to reduce Iran's oil exports has a consequence.
"Iran has said repeatedly that if its oil exports are stopped, then it's going to stop other exports in the region.
"But again, this is about smuggled fuel, so this particular case might be different from the seizures from before in that respect.
"We are seeing something like a war of attrition where both sounds are looking for a face-saving exercise.
"I believe Iran has more stamina than the US believes.
"The upcoming weeks will see whether the Iran nuclear deal can be saved. Otherwise, unfortunately, we might see more escalation - as we have in the past weeks and months."