Britain has issued the highest possible security alert to British shipping companies operating off the coast of Yemen, an expert said, amid a worldwide terror alert focused on the country.

Mr Neil Roberts, a senior insurance underwriter at Lloyd's Market Association, said the Department for Transport had issued a "level three" warning about Yemen on Monday.

Under the International Ship and Port Facility Security (ISPS) code, level three is "exceptional", suggesting a "probable or imminent risk of a security incident".

Insurers have listed Yemen as a high-risk area for at least the last five years, requiring shipping companies to alert their underwriters before they head to the country. (Source: SPH)