British maritime security firm Ambrey said on Tuesday it received information of a potential boarding attempt 71 nautical miles west of Yemen's Aden port city, adding that the attack was unsuccessful and all crew are safe.

"A vessel in the vicinity received VHF communication of a vessel 'under piracy attack' at the location. Half an hour later, collision aircraft arrived on scene to search the area," the security firm said in an advisory note.

Ambrey corroborated that three merchant vessels were approached by small boats while transiting eastbound 71 nautical miles southwest of Yemen's Aden.

A Liberia-flagged bulk carrier was approached within 0.5 miles by a Yemeni-style skiff, the advisory added.

The vessel conducted evasive manoeuvres by changing course and increasing speed, Ambrey said.

One of the other two vessels, a Liberia-flagged tanker, issued a distress call, claiming an attack, but it stated later the "boarding attempt" was aborted and the vessel continued its voyage.

There are industry fears of a spillover in attacks by other groups amid a growing number of attacks by Iran-backed Houthis from Yemen on commercial shipping in the Red Sea in support of Palestinians in Gaza, shipping sources said.