A merchant vessel reported being approached with the use of small arms fire in waters 92 nautical miles northeast of Eritrea's Massawa port in Red Sea waters adjacent to Yemen's coast, British maritime security firm Ambrey said on Thursday.The United Kingdom Maritime Trade Operations (UKMTO) said shortly after that it received a sighting report of a small boat with armed persons onboard, operating in close proximity to a small coastal freighter, approximately 95 nautical miles northeast of Massawa.Authorities are investigating, UKMTO's advisory note added.