It was the second such action this week, as the Trump administration ramps up pressure on Tehran.
A British naval agency said the two vessels had come under attack near the strait, as a U.S. blockade on Iran’s ports continued.
Hours after President Trump extended a cease-fire, Tehran appeared to be exerting its authority in the contested waters near the strait.
In a thinly veiled critique of the war in Iran, China’s leader said the world could not risk reverting “to the law of the jungle.”
Ship-tracking data showed that several vessels, including some that had been docked at Iranian ports, had moved through the strait as the U.S. military began its blockade.
The vessels exited the Strait of Hormuz on Monday, hours before a U.S. naval blockade took effect.
The attack damaged the hull, the tanker’s owner said. No oil spill was detected, according to the authorities in the United Arab Emirates.
The ship was struck near an Emirati port, in the first such attack in five days. The United Arab Emirates also said it was intercepting Iranian drones and missiles.
A fifth of the world’s oil passes through the strait, making it a critical choke point in global commerce.
The United States said this week that it had attacked 16 Iranian mine-laying vessels near the Strait of Hormuz. In the 1980s, Iranian mines damaged oil tankers and a U.S. Navy warship.