India, July 18 -- A chemical tanker was boarded by an armed group off the coast of Yemen on Friday while it was transiting in the Gulf of Aden, the British military said.

The United Kingdom Maritime Trade Operations Centre (UKMTO) said military authorities had reported that the vessel was boarded by "unauthorised personnel" south of al-Mukalla province in Yemen. Ambrey, a British maritime security firm, said Somali pirates are believed to have boarded the tanker, which does not have an armed security team on board.

The firm said a Korean naval vessel was on its way to assist the tanker, which issued a distress call while heading westbound. The data tracker, Maritime Traffic, showed that the Tanzania-flagged oil and chemical tanker Asana...