LONDON Missile attacks from Yemen on Western military craft risk spilling over into nearby busy sea lanes which could disrupt oil supplies and also other vital goods passing through the tense area, shipping and insurance sources say.
While shipping companies have yet to divert ships, there are growing worries that any further escalation could hinder oil supplies and potentially lead to higher insurance costs for shipments.
The route is among the world's busiest and used by major shipping groups such as container line Maersk (MAERSKb.CO) and oil tanker carriers including Norway's Frontline (FRO.OL) and Iran's NITC, which has benefited this year from the lifting of international sanctions on Tehran.
A ship insurance source said some ships coming into Yemeni ports were already switching off their tracking systems, which allow anyone to monitor their movements via the Internet, due to the violence in the country.
The source said war risk insurance premiums to Yemeni ports such as Hodaida in the north, already amounted to hundreds of thousands of dollars of cover for every vessel.
A U.S. Navy guided missile destroyer was targeted on Sunday in a failed missile attack from territory in Yemen controlled by Iran-aligned Houthi rebels, a U.S. military spokesman said, although the ship was not hit.
The Houthi movement on Monday denied its forces had carried out a missile attack on a U.S. warship.
The attempted strike on the USS Mason came just a week after a United Arab Emirates vessel was attacked by Houthis and suggests growing risks to the U.S. military from Yemen's conflict.
The attacks took place around the Bab al-Mandab gateway though which nearly four million barrels of oil are shipped daily to Europe, the United States and Asia.
"The Bab al-Mandab is a vital artery for shipping," said Gavin Simmonds, security and commercial policy director with the UK Chamber of Shipping.
"International shipping is totally dependent on the ability of the international community to provide safe transit of commercial vessels along major sea lanes."
The UN last week said it took threats to shipping around Bab al-Mandeb "extremely seriously".
"It is a deteriorating situation and it is worrying that this longer range weaponry is being used in the area," said Phillip Belcher marine director with INTERTANKO, an association which represents the majority of the world's tanker fleet.
Yemen has a 1,900-km (1,181 mile) coastline that also juts into the Gulf of Aden and Red Sea - a vast area to police given international navies are already stretched combating Somali piracy in the region, which had been contained in recent years.
The U.S. Office of Naval Intelligence said in a report last week commercial ships in the Red Sea, Bab al-Mandab and Gulf of Aden areas should operate "under a heightened state of alert as increasing tensions in the region escalate the potential for direct or collateral damage to vessels transiting the region".
Riyadh is leading a coalition of Arab states which began launching air strikes against the Houthis in Yemen 18 months ago to restore to power ousted President Abd Rabbu Mansour al-Hadi.
The war has killed at least 10,000 people and brought parts of Yemen, by far the poorest country in the Arabian peninsula, to the brink of starvation. Both sides accuse the other of war crimes.
(Editing by David Evans)