The Iranian Navy seized two US Navy maritime drones in international waters in the Red Sea on Thursday.

The drones were eventually released, but a US defense official says the incident looks like an escalation of Iranian hostile actions against the United States.

Earlier this week, a similar incident occurred in the Persian Gulf. “The fact that this happened two days after their unsuccessful attempt in the Arabian (Persian) Gulf looks to be an escalation,” the official said

The incident began Thursday, the official said, when the Iranian Navy ship was observed taking two US drones out of the water “in an attempt to steal them,” according to the official. The US then quickly moved in with two nearby destroyers, the USS Nitze and USS Delbert D. Black, as well as two helicopters and communicated by radio to demand the drones be returned.

The Iranians agreed but asked to wait until daylight on Friday for safety reasons which the US agreed to, the official said.

The unmanned maritime vessels, known as Saildrone Explorers, had been operating in international waters in the southern Red Sea, four miles away from the nearest maritime traffic lane, according to US Central Command. The unarmed drones had been operating in the area for more than 200 days without incident, Central Command said, and they were taking unclassified photos of the environment.

Iranian state television broadcasted video showing the drones being pushed back into the water from the deck of the Iranian warship.

Iran's state TV said the Iranian Navy seized the drones while carrying out an anti-terrorism mission in the Red Sea. “The destroyer Jamaran seized two vessels on Thursday to prevent any possible accident ... the two vessels were released after international shipping lanes were secured and a warning was issued to the US fleet,” state TV said.

The incidents come at a sensitive time with negotiations over a revived nuclear agreement appearing to falter. On Thursday, the US State Department said Tehran's latest reply to a European Union proposal to resurrect the deal was “not constructive.”

The US official noted that unprofessional interactions with the Islamic Republic of Iran Navy are rare. When other unprofessional incidents have occurred, they have typically involved Iranian Revolutionary Guard naval ships (IRGC), not the regular Iranian Navy.

IRGC ships and small boats have had multiple unprofessional interactions with the US Navy in recent years.

Earlier this week, the US Navy prevented an Iranian ship from capturing an American maritime drone in the Persian Gulf in what a senior US commander called a “flagrant” and “unwarranted” incident.

While US forces in the region were transiting international waters Monday, they saw an Iranian Islamic Revolutionary Guard Corps Navy support ship, Shahid Baziar, towing a US-operated maritime drone, also known as a Saildrone Explorer unmanned surface vessel.

A US Navy patrol coastal ship, USS Thunderbolt, was “operating nearby and immediately responded,” the Navy said. After the Iranians attached a line to the maritime drone, US forces in the area communicated directly with the Iranians to say they wanted the drone back, and the Iranians eventually disconnected the tow line.

The US is increasingly using commercially available drones that it leases to carry out maritime surveillance. The official said because it involves commercial technology, there is currently no concern Iran has gained access to classified technology. (CNN)

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