Iran's paramilitary Revolutionary Guard forces have seized a foreign oil tanker with a crew of 12, which they accuse of smuggling oil in the Persian Gulf, Iran's state TV reported Thursday. The report did not name the vessel, but Iranian state TV earlier said the Guard came to the tanker's aid when it sent a distress call before impounding it, according to the Reuters news agency.

The move comes days after an oil tanker based in the United Arab Emirates -- the Panamanian-flagged MT Riah -- disappeared off trackers in Iranian territorial waters. Later Thursday, Iranian media aired video it said was released by the Revolutionary Guard of a ship which appeared to be the Riah.

"We are aware of the reports but have nothing on this issue," a U.S. defense official told CBS News in a statement. The seizure was the latest in a series of dramatic developments as tensions mount between the United States and Iran over the unravelling nuclear deal between Tehran and world powers.

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No other nation reported receiving a distress call from the Riah, CBS News senior national security correspondent David Martin says, which was seen being escorted by Iranian naval vessels after the transponder that automatically reports its location was switched off early Sunday.

The Riah was last reported to be anchored off Iran's Qeshm island, which hosts a number of bases belonging to the Islamic Republic's elite Revolutionary Guard force. The Iranian state media report said the seized oil tanker was intercepted south of Iran's Larak Island in the Strait of Hormuz. Larak is a smaller island just southeast of Qeshm.

Iran's state television did not identify the seized vessel or nationalities of the crew, but said it was intercepted on Sunday. It said the oil tanker was involved in smuggling some 264,000 gallons of fuel from Iranian smugglers to foreign customers.

The 190-foot Riah, which was based in the United Arab Emirates, typically made trips from Dubai and Sharjah on the UAE's west coast before going through the Strait of Hormuz and heading to Fujairah on the UAE's east coast.

Attacks on oil tankers and Iran shooting down a U.S. military surveillance drone have added to fears of an armed conflict breaking out between the two countries. The U.S. has sent thousands of additional troops, nuclear-capable B-52 bombers, and advanced fighter jets into the Mideast amid the heightened tensions.