Unidentified armed men have boarded a Hong Kong-flagged oil tanker off the coast of Iran near the strategic Strait of Hormuz, a British monitoring organization and a private intelligence firm reported.
The United Kingdom Maritime Trade Organization said the vessel was boarded on April 14 while anchored just off the Iranian coast in the Sea of Oman, but added that the ship was later released.
The organization urged vessels in the area to "stay vigilant."
Dryad Global, a private maritime intelligence firm, said it was unclear whether the vessel had been in distress or was being assisted by Iran.
The company identified the tanker as the Hong Kong-flagged SC Taipei on its way to Al-Jubail in Saudi Arabia. It said the 22 crew members aboard were all Chinese.
The U.S. Navy’s Fifth Fleet based in Bahrain has not immediately commented on the reported incident, which comes amid heightened tensions between the United States and Iran in the region.
Iran's Islamic Revolutionary Guards Corps (IRGC) has harassed or seized a number of vessels over the last year in a move viewed by analysts as a way to exert pressure on the United States and its allies over crushing U.S. economic sanctions.
Iran is also suspected of planting limpet mines on six ships in the Gulf of Oman in May and June of 2019.
Dryad Global said "it cannot nor should not be ruled out" that Iran attempted an operation on April 14 against the Hong Kong-flagged ship "in haste," and aborted the mission out of political concerns.
"While Beijing is not responsible for Hong Kong vessels, there is a realistic possibility that China would view the detention of a Hong Kong vessel as a proxy assault on its own sovereignty," the company said. "At a time when China still buys Iranian oil, and Iran has few international friends, such a move would be highly irregular, and would not further Iran’s interests."