A tanker was struck by an unknown projectile in its port bow off the coast of Oman, the United Kingdom Maritime Trade Operations (UKMTO) said on Saturday.The incident occurred on Friday, around six nautical miles (11km) east of Oman, according to the advisory.Crew safe, no environmental damage reportedUKMTO said all crew members aboard the vessel are safe and there has been no reported environmental impact.The tanker is continuing its journey towards its next port of call while authorities investigate the incident.Vessels advised to stay cautiousMaritime authorities have urged ships in the area to exercise caution and report any suspicious activity to UKMTO.Regional shipping tensionsThe alert comes amid continued security concerns in key maritime routes in the region, where shipping incidents have been periodically reported and vessel traffic disruptions have raised concern among operators.