A British maritime security agency on Thursday said it was investigating reports of an attack on a vessel off Yemen's lawless coast.
UK Maritime Trade Operations said the reported attack happened 34 nautical miles southwest of the Red Sea port of Hodeida, held by Houthi rebels.
"Investigations are ongoing," it added.
The UKMTO is involved in anti-piracy operations and is part of the Royal Navy, which is coordinating surveillance in the region.
Previous attacks have been blamed on Somali pirates but have fallen in recent years as a result of international security operations.
Yemen is in the grip of a devastating humanitarian crisis because of fighting between Iran-supported Huthi rebels and the Saudi-backed government.
More than 150,000 people have died in the war and millions have been displaced, according to United Nations estimates.