Two vessels sustained damage after being hit with missiles and a sea drone off Yemen's Hodeidah port early on Tuesday, maritime security agencies and sources monitoring the area said.
Both vessels reported that their crews were safe.
One of the vessels, which sources said was a Panama-flagged tanker, reported being hit by an Uncrewed Surface Vessel (USV) 64 nautical miles northwest of Hodeidah, the United Kingdom Maritime Trade Operations agency said.
It was damaged on its port side ballast tank, British security firm Ambrey said, adding that it was proceeding to its port of call.
The vessel had earlier reported seeing four splashes on the water close to it, which a maritime security source said were attempted missile attacks.
The second vessel, which sources said was a Liberia-flagged bulker, sustained damage after it was hit by a missile about 97 nautical miles northwest of Hodeidah, Ambrey and maritime security sources said. The firm said it was bound for Suez.
Authorities were investigating both incidents. There was no immediate claim of responsibility for the attacks.
Yemen's Iran-aligned Houthi militants have launched attacks on international shipping near Yemen since last November in solidarity with Palestinians in the war between Israel and Hamas.
Reporting by Yomna Ehab in Cairo, Tala Ramadan and Jana Choukeir in Dubai, Renee Maltezou and Yannis Souliotis in Athens