A speedboat with armed men aboard approached two vessels transiting off the coast of Yemen's Red Sea port of Hodeidah, an advisory note from British maritime security company Ambrey said on Wednesday.
Britain's Maritime Trade Operations (UKMTO) agency said it had received reports of an incident in the vicinity of the Bab al-Mandab Strait, without giving more details.
Yemen's Iran-aligned Houthis have waded into the Israel-Hamas war raging over 1,000 miles (1,620 km) away, attacking vessels in vital shipping lanes and firing drones and missiles towards Israel in support of Gaza's Palestinian militants.
Operating from their seat of power in the Yemeni capital Sanaa, Houthi forces have been targeting vessels allegedly owned by Israeli businessmen or companies, or ships headed to ports in Israel, and obstructing their passage through the Bab al-Mandab Strait at the southern end of the Red Sea.
Ambrey said a Marshall islands-flagged chemical tanker reported an "exchange of fire" with a speedboat 55 nautical miles (around 102 kilometres) off Hodeidah, adding that the boat approached the tanker and initiated the gunfire at a distance of 300 metres (1,000 feet).
It said the tanker was hailed by an entity claiming to be the Yemeni Navy that asked the vessel to alter course but a "coalition" warship advised the ship to maintain it.
Ambrey did not clarify which coalition it was referring to. Coalition Task Force (CTF) Sentinel, the operational arm of the International Maritime Security Construct (IMSC), is known to operate in the region. IMSC was formed in July 2019 in response to an increase in threats to navigation and the flow of trade.
Shortly after the tanker incident, Ambrey said, the speedboat approached a Malta-flagged bulk carrier 52 nautical miles off Hodeidah's shores, adding that it would provide updates as relevant.
Separately, UKMTO reported an incident in the Arabian Sea about 90 nautical miles off the Omani coastal town of Duqm. It did not give further details but advised ships to transit with caution and report any suspicious activity.
