A Singapore-flagged container ship has sunk after being struck by an unknown projectile while transiting the Strait of Hormuz, according to Singaporean authorities.
All 21 crew members of GFS Pride were evacuated and no injuries were reported after the attack on Tuesday, which caused damage and a fire, the Maritime and Port Authority of Singapore said.
Another Singapore-flagged container vessel, GFS Giselle, sustained hull damage after being hit by a projectile on Wednesday but was able to reach a safe anchorage with all 22 crew, it added.
Iran's Revolutionary Guards said a ship hit naval mines and sank while passing through what they called an "unauthorised" route in the Strait of Hormuz.
The Guards released photos that appeared to show a plume of black smoke rising from a container vessel that was still afloat but down by the stern. In other photos, dozens of containers and their contents could be seen floating in the water.
The Hydrographer of Pakistan warned mariners that GFS Pride had sunk 4 nautical miles (7.4km) north-west of Ras al-Sheikh Masud in Oman's Musandam Peninsula.
Meanwhile, the United Kingdom Maritime Trade Operations (UKMTO) agency said that two unnamed container ships had reported being struck by unknown projectiles while transiting the Strait of Hormuz between 16:40 and 17:00 GMT on Tuesday.
Both vessels sustained minor damage and were able to continue their passages, it added.
Merchant vessels have come under repeated attack in the Strait of Hormuz - which connects the Gulf to the Gulf of Oman and Arabian Sea - and elsewhere in the Middle East since the US and Israel's war with Iran began in February.
At least 24 seafarers have been killed in 106 confirmed incidents, according to the UN's International Maritime Organization.
The Malta-flagged container ship Safeen Prestige, which was attacked near Oman on 4 March, is the only other vessel reported to have sunk in that time.
However, maritime risk management group Vanguard said on Wednesday that the Antigua and Barbuda-flagged bulk carrier Cape Dao was reported to be sinking after an unsuccessful rescue attempt, according to Reuters news agency.
One seafarer was killed when the Cape Dao's bridge and accommodation area were hit by an unknown projectile as it transited through the Strait of Hormuz, north-east of Khasab, Oman, on 23 September.
The Strait of Hormuz, through which a fifth of global oil and gas shipments usually pass, was effectively closed after the start of the Iran war due to Iranian missile and drone attacks on commercial vessels and a US naval blockade of Iranian ports.
The US and Iran reached a preliminary agreement to end the war and reopen the strait in June, but it collapsed within weeks after Iranian attacks on shipping resumed and the US reinstated its blockade.
Iran insisted it would not give up some measure of control over the waterway and began targeting vessels using a southern route through Omani waters that avoids its preferred route through Iranian waters.
To keep exports flowing from Gulf Arab states, the US military has been providing protection for tankers shuttling oil through the Strait of Hormuz.
Last month, crude exports through the waterway rose to around 80% of pre-war levels of 16 million barrels per day (bpd) on average, according to analysts from shipping data company Kpler, despite an increase in attacks on shipping.