The US navy said Tuesday that the 18-day biennial International Maritime Exercise (IMX) since Monday includes 50 vessels and 9,000 personnel from more than 60 entities.

With more than 80 drones, it is also the world's largest unmanned drill, it added from Bahrain, where the 5th Fleet is headquartered.

The excercise comes at a time of regional tensions over Iran's nuclear programme and Yemeni rebels' recent targeting of Saudi Arabia and the United Arab Emirates with missiles and drones.

It includes a number of countries -- among them Saudi Arabia, Pakistan, Oman and Yemen -- that do not have formal diplomatic relations with Israel.

However, Saudi Arabia and Israel share the same desire to contain their common foe Iran.

Israeli army spokesman Avichay Adraee tweeted Monday that Israel would "for the first time take part" in the IMX drill.

In November, the UAE and Bahrain launched joint naval exercises with Israel for the first time.

Yemen's Iran-backed Huthi rebels targeted the UAE three times in January with drones and missiles, killing three foreign workers in the first attack on January 17.

Earlier in the month, the rebels seized a UAE-flagged ship in the Red Sea, saying it was carrying weapons -- a claim denied by the Emirates.

The US navy said in January it had stopped a ship carrying 40 tons of a fertiliser that can be used to make explosives as it travelled from Iran along a route previously used to smuggle weapons to the Huthis.

In December, it had seized 1,400 AK-47 rifles and ammunition from a fishing boat it claimed was smuggling weapons from Iran to Yemen.