Black smoke rose off the Saudi port of Yanbu after an unspecified incident in the Red Sea, authorities said, as one private security firm warned of a possible attack on a ship.
Details remained scarce, but the incident comes after a series of attacks on shipping across the Middle East amid a shadow war between Iran and Israel amid negotiations between Tehran and world powers over its tattered nuclear deal.
Saudi Arabia did not immediately acknowledge the incident.
United Kingdom Maritime Trade Operations, run by the Royal Navy, simply said it was “aware of reports of an incident” and that investigations were continuing.
Private maritime security firm Dryad Global said it had received reports that a ship had been attacked.
Maritime security firm Neptune P2P Group reported that black smoke was seen billowing near the south entrance of Yanbu port.
British maritime security firm Ambrey reported an “incident” off western Saudi Arabia between the ports of Yanbu and Rabigh.
Earlier on Tuesday morning, smoke was seen rising from a vessel off the oil shipping port of of Yanbu, the firm reported. Multiple tankers remained anchored or drifting in the area.
King Fahd port control at Yanbu broadcast a message by marine VHF radio warning vessels to increase their level of alertness and monitor for any suspicious activity, Ambrey said.
The incident came as the US navy released footage of a tense encounter between American and Iranian warships in the Persian Gulf earlier this month, the first such incident in about a year.
The footage showed a ship commanded by Iran’s paramilitary Revolutionary Guard cut in front of the USCGC Monomoy on April 2, causing the Coast Guard vessel to come to an abrupt stop with its engine smoking.
The Guard did the same with another Coast Guard vessel, the USCGC Wrangell, said Commander Rebecca Rebarich, a 5th Fleet spokeswoman.
Iran did not immediately acknowledge the incident in the southern reaches of the Persian Gulf, which resulted in no injuries or damage.