New Delhi, July 18 -- DUBAI - Armed men boarded the Tanzanian-flagged chemical tanker Asana in the Gulf of Aden on Friday, seizing control of the vessel in what maritime security authorities and regional officials believe was a Somali piracy attack rather than a Houthi operation - the latest in a sequence of incidents that has begun rewriting risk assessments for one of the world's most critical waterways.

The UK Maritime Trade Operations agency, the Royal Navy unit that coordinates commercial shipping advisories across the region, confirmed "a vessel was boarded by unauthorized personnel while transiting east." Yemeni coastguard officials placed the boarding approximately 26 nautical miles off Hadramawt province, with one early report d...