British security firm Ambrey said it had received information indicating that a vessel was attacked on Sunday in the Gulf of Aden about 102 nautical miles southwest of Mukalla in Yemen.
"Vessels in the vicinity were advised to exercise caution and report any suspicious activity," the firm said. It did not say who was responsible for the attack or give further details.
Yemen's Iran-aligned Houthi militias have staged months of attacks on shipping in the Red Sea region in support of Palestinians in the Gaza war.
Separately, a missile landed near a vessel in the Gulf of Aden on Sunday but there was no damage to the ship or injuries to crew in the incident, 59 nautical miles southwest of the Yemeni port of Aden, the United Kingdom Maritime Trade Operations (UKMTO) agency said.
"The Master of the vessel reports a missile impacted the water in close proximity to the vessel’s port quarter," UKMTO said in an advisory note. "No damage to the vessel reported and crew reported safe," it added.
It did not say who fired the missile or give further details.
The Houthi attacks have disrupted global shipping through the Suez Canal, forcing firms to re-route to longer and more expensive journeys around southern Africa. The United States and Britain have launched strikes on Houthi targets in Yemen.
