On a day that's witnessed serious escalation amid already soaring tensions in the Persian Gulf, Iran has confirmed the vessel it earlier said its IRGC forces seized for "smuggling" oil is in fact Panamanian-flagged oil tanker MT Riah which had disappeared near Iranian waters starting last weekend. State TV aired dramatic footage showing multiple IRGC fast-boats swarming the clearly marked vessel in the Strait of Hormuz.

On Tuesday international reports described the Riah as a tanker based in the United Arab Emirates and cited US intelligence officials to say Iran's navy had forced the vessel into waters near Iran's coast starting late Saturday night. Iran had initially denied the accusations that it had detained the vessel.

But now Foreign Minister Mohammad Javad Zarif has acknowledged the vessel is now being detained by Iran for "smuggling":

“We do this (inspecting ships) every day. These are people who smuggle our oil,” Iran's Press TV quoted Iranian Foreign Minister Mohammad Javad Zarif as saying, adding: “It was a small ship used to smuggle 1 million litres - not 1 million barrels - of crude oil.”

It's clear that Tehran is attempting to ramp up the pressure on Washington and drive up global oil prices, while also potentially in the beginning phase of making good on its long time threat to cut off global shipping through the vital oil passageway.

State run ISNA had earlier in the day described, "A foreign vessel smuggling one million liters of fuel in the Lark Island of the Persian Gulf has been seized," and said its navy detained it starting Sunday.

Iran's Press TV had previously issued the following details:

The incident took place to the south of the Iranian Lark Island on Sunday. IRGC naval forces, which were patrolling the waters on an anti-smuggling mission, acted against the vessel in a “surprise” operation upon ascertaining the nature of its cargo and securing the required legal approval from Iranian authorities. The ship had loaded the fuel from Iranian dhows and was about to hand it over to other foreign vessels in farther waters. The vessel, which had 12 foreign crewmembers aboard at the time of the mission, is capable of carrying two million liters of fuel. The statement hailed the naval forces’ “perceptiveness” in frustrating the smuggling effort. It added that the crime had invoked due legal proceedings.

Days ago Iran vowed to "answer" the UK's seizure and detention of the 'Grace 1' which had been transporting 2 million barrels of Iranian oil to Syria. The Royal Marines had boarded it in the Strait of Gibraltar and arrested its crew.

Tehran condemned it as an act of "piracy" and warned the UK it would respond in kind. Thursday's so far mysterious vessel seizure announced by the IRGC could be the start of the promised coming retribution.

Meanwhile, late in the day Thursday President Trump announced that the amphibious assault ship, the USS Boxer, shot down an Iranian drone in the Strait of Hormuz in a defensive action.

But strangely, Iran's FM Zarif claimed not be aware of any drone downing following Trump's announcement, according to Reuters. “We have no information about losing a drone today,” Zarif told reporters at the United Nations.