SINGAPORE: Vessel crossings via the Strait of Hormuz dropped further at the start of the week, shipping data showed, as caution grew following a fresh exchange of attacks between the United States and Iran.A total of four commodity vessels crossed ‌the strait ⁠on Monday, ⁠mostly on the Iranian route, down from seven the previous day, ​Kpler data showed.Also read: US military completes its latest strikes on Iran, marking the 10th successive night of attacksThe four vessels included two tankers that exited ​the strait as well as two vessels that entered.The two vessels that exited comprised a tanker that was carrying ​petrochemicals and one that was ⁠empty.Meanwhile, the ‌two vessels that entered the strait ​included a bitumen ​tanker and an oil tanker.There were ⁠no visible very large crude carrier (VLCC) or liquefied ​natural gas tankers passing through the strait ​on Monday.Shipping tensions intensified further as Yemen's Iran-aligned Houthis said on Monday they were imposing a naval blockade on Saudi Arabia, a move that threatens to disrupt global energy supplies beyond the Gulf.The United Kingdom Maritime ‌Trade Operations agency said on Tuesday it had received multiple reports that a tanker had messaged ​that it ​had been ⁠struck by an unknown projectile in the Strait of Hormuz.Separately, Greek shipping company Dynacom Tankers said two of its managed vessels ​were hit by projectiles of unknown origin on Monday while sailing off the coast of Oman, while a third tanker was struck by a drone at Russia's Novorossiysk CPC terminal in the Black Sea.