There have been several reports of vessels being attacked by Iran on Saturday.
Two Iranian gunboats opened fire on a tanker in the strait, the UK Maritime Trade Operations (UKMTO) said.
A container ship was also hit by “an unknown projectile” off the north-eastern coast of Oman, damaging some containers, according to the UKMTO.
Separately, at least two merchant vessels said they were hit by gunfire as they attempted to cross the strait, sources told news agency Reuters.
India’s foreign ministry said it had summoned the Iranian ambassador to convey its “deep concern at the shooting incident earlier today involving two Indian-flagged ships in the Strait of Hormuz”.
Data from tracking site MarineTraffic showed some vessels were able to make it through the strait while it was briefly open. Others were forced to change their route after the IRGC denied them access.
About 20% of the world’s oil and liquefied natural gas (LNG) is usually transported through the strait, but the number of ships making the journey has dramatically decreased during the recent conflict, which began when the US and Israel attacked Iran on 28 February.
The narrow chokepoint connects the Gulf to the Arabian Sea and is the only way to reach several oil-producing states by sea. The crisis has seen the price of a barrel of oil surge above $100 ($74) at points.
Iran has previously threatened to attack tankers and other ships, as well as warning it had laid mines.