THE US Department of Transportation Maritime Administration (Marad) has warned merchant shipping near Yemen and Somalia to be extra careful when navigating in the region, reports Bloomberg.

"Exercise caution when transiting these areas and remain cognizant of evolving threats in this region," said the Marad alert.

"There are still considerable risks faced across the broader market with threats of collateral damage and misidentification always present," said Munro Anderson, head of operations at Vessel Protect, a specialist marine war risks underwriter.

Most insurers already charge extra premiums for sailing through those waters and those charges could increase further if the attacks continue.

"Such events stand as evidence of wider risks to the broader commercial market when trading in such areas," said Mr Anderson, referring to the risk of vessels being mistakenly targeted.

The recent burst of activity risks disruption of a route that's critical to global trade in everything from commodities to manufactured goods. The waters in question are unavoidable for ships sailing between Europe and Asia via the Suez Canal.

Houthis forces seized of the Galaxy Leader car carrier two weeks ago while a Liberia-flagged chemicals tanker Central Park was targeted over more recently.

Both have Israeli connections. At the same time, there have also been at least four other suspicious approaches to ships in the Indian Ocean in the past few weeks - many of them taking place in the Red Sea or the Gulf of Aden - according to the Royal Navy.