A merchant vessel reported being hit by a projectile in the Red Sea off the coast of Yemen on Thursday, British security firm Ambrey said.
No injuries or damage were reported in the incident, which occurred 84 nautical miles west of Yemen's port of Hodeidah, Ambrey added.
The vessel was headed for the city of Dammam in Saudi Arabia.
The United Kingdom Maritime Trade Operations also said it had received a report of the incident.
UKMTO added that the vessel and crew were reported to be safe, and the vessel was proceeding to its next port of call.
"The nature of the attack is reported as a waterborne improvised explosive device," UKMTO said in an advisory note.
International shipping has been disrupted by attacks in the region launched by Yemen-based Houthi militants since November.
Many vessels have since opted to avoid the Red Sea route to the Suez Canal, taking the longer journey around the southern tip of Africa instead.
The Iran-aligned Houthis say the attacks are in solidarity with Palestinians in the war between Israel and the terrorist Islamist group Hamas.