Dubai, United Arab Emirates -- Tracking data shows an oil tanker based in the United Arab Emirates traveling through the Strait of Hormuz drifted off into Iranian waters and stopped transmitting its location over two days ago, raising concerns Tuesday about its status amid heightened tensions between Iran and the U.S.

Iran vowed on Tuesday, as the world wondered where the tanker had gone, that the seizure of one of its own crude oil tankers by British military forces earlier in July would not go "without a response."

It isn't clear what happened to the Panamanian-flagged oil tanker Riah late on Saturday night. However, its last position showed it pointing toward Iranian waters and the Islamic Republic's Qeshm island, which hosts a number of bases belonging to Iran's elite Revolutionary Guard forces. Oil tankers have previously been targeted as the Persian Gulf region took center stage in a crisis over Iran's unraveling nuclear deal with world powers.

A May 30, 2012, file photo shows fishermen crossing the waters off Fujairah, United Arab Emirates, near the Strait of Hormuz, as a commercial vessel sails in the background. AP

The Riah, a 190-foot oil tanker, typically made trips from Dubai and Sharjah on the UAE's west coast before going through the strait and heading to Fujairah on the UAE's east coast. However, something happened to the vessel after 11 p.m. on Saturday, according to tracking data. Adding to the mystery was the fact that nobody appeared to claim ownership of the Riah.

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Capt. Ranjith Raja of the data firm Refinitiv told The Associated Press on Tuesday that the tanker hadn't switched off its tracking in three months of trips around the UAE.

"That is a red flag," Raja said.

Iranian officials have not said anything publicly about the ship, nor have officials in the UAE. The U.S. Navy's 5th Fleet, which oversees Mideast waters, declined comment.

The ship's registered owner, Dubai-based Prime Tankers LLC, told the AP it had sold the ship to another company called Mouj Al-Bahar. A man who answered a telephone number registered to the firm told the AP it didn't own any ships.

Pan-Arab television network Al-Arabiya reported on Tuesday that officials in the UAE had said it was not owned by any entity in the country.

Iran vows to answer "piracy"

Separately, Iran's Supreme Leader Ayatollah Ali Khamenei said Tuesday his country would retaliate over the seizure of an Iranian supertanker carrying 2.1 million barrels of light crude oil. The vessel was seized with the help of British Royal Marines earlier this month off Gibraltar.

Khamenei called the seizure of the ship "piracy" in a televised speech Tuesday.

"God willing, the Islamic Republic and its committed forces will not leave this evil without a response," he said.

British Foreign Secretary Jeremy Hunt said Saturday that Britain will facilitate the release of the ship if Iran can provide guarantees the vessel, called the Grace 1, will not breach European sanctions on oil shipments to Syria.

Nuclear deal unravelling

The concern about the Riah comes as Iran continues its own high-pressure campaign over its nuclear program after President Donald Trump unilaterally withdrew America from the accord over a year ago.

Recently, Iran has inched its uranium production and enrichment over the limits of its 2015 nuclear deal, trying to put more pressure on Europe to offer it better terms and allow it to sell its crude oil abroad.

However, those tensions also have seen the U.S. send thousands of additional troops, nuclear-capable B-52 bombers and advanced fighter jets into the Mideast. Mysterious attacks on oil tankers and Iran shooting down a U.S. military surveillance drone has added to the fears of an armed conflict breaking out.