Iran seized a foreign-registered oil tanker in the Persian Gulf, the country’s state-run media announced Thursday. The ship was captured Sunday.

Twelve crew members were on the Panamanian-flagged vessel when it was taken near the Strait of Hormuz. The Iran Revolutionary Guards Corps, a powerful organization with links to the military and business, said the tanker tried to smuggle 1 million liters of oil. Nationalities of the crew members were not known.

The incident was reported by Iran’s Press TV and other media outlets.

U.S. Central Command in Bahrain, where the U.S. Navy's Fifth Fleet is based, said it was aware of what Iran reported but had no response to it yet. Iran’s Foreign Ministry said it was trying to get more information about the tanker and why it was seized.

Iran’s semi-official Fars news agency said the tanker was used to smuggle oil from Iran. Sunday, Iran said it helped a foreign-flagged oil tanker in the Strait of Hormuz – one of the world’s major conduits for seaborne oil transportation – that ran into technical difficulties.

Press TV released video footage showing Iranian navy boats circling the ship, called Riah. It said the vessel was seized for smuggling oil.

This week, Iran said it towed the Riah, which is based in the United Arab Emirates, into Iranian waters for repairs after the ship sent out distress signals. Two Emirati oil tankers were among four tankers attacked in May in acts of sabotage that the United States blamed on Iran. Iran denied being behind the attacks.

Iranian Foreign Minster Mohammad Javad Zarif told reporters in New York on Thursday that Iran would offer a deal to the U.S. in which it would offer it enhanced inspections of its nuclear facilities in return for the permanent lifting of economic sanctions.

Zarif characterized the offer as a “substantial move.” Zarif said the seized oil tanker was an ordinary maritime policing matter, saying “we do this kind of thing every day.”

The White House did not immediately react, but, in response to a reporter’s question, President Donald Trump said a “big event just happened in Iran.” It wasn’t clear if Trump was referring to Zarif’s apparent offer.

Tensions are high between the United States and Iran after the Trump administration pulled out of a nuclear deal between Iran and world powers and reimposed sweeping economic sanctions. Iran pledged to seize a British oil tanker after the Royal Navy impounded an Iranian oil tanker off the coast of Gibraltar, in the Mediterranean Sea, that British officials suspected was trying to smuggle Iranian oil to Syria in contravention of European Union sanctions.

Iran denied the oil tanker was on its way to Syria.

The Pentagon is preparing to send hundreds of troops to Saudi Arabia in the latest show of force toward Iran, CNN reported Wednesday. The move is part of Washington's broader plan to bolster U.S. forces in the region amid deteriorating relations with Iran, which shot down a U.S. drone last month.

A Navy carrier strike force and other military equipment has been deployed. Britain's Royal Navy also increased its presence in the Gulf.