Dubai: The British military said a ship caught fire Sunday after being hit by an unknown projectile off the coast of Qatar.

The United Kingdom Maritime Trade Operations Centre said the attack caused a small fire on the bulk carrier, which was extinguished.

The attack happened 23 nautical miles (43 km) northeast of Qatar's capital, Doha, the UKMTO said.

There were no reported casualties, it said.

It was the latest attack on vessels in the Persian Gulf since a shaky ceasefire stopped fighting between the United States and Iran.

There have been several attacks against ships in the Persian Gulf over the past week. On Friday, the US struck two Iranian oil tankers after it said the tankers were trying to breach its blockade of Iran's ports.

Iran's Revolutionary Guard Navy has warned that any attack on Iranian oil tankers or commercial vessels would be met with a "heavy assault" on one of the US bases in the region and enemy ships.

US President Donald Trump has reiterated threats to resume full-scale bombing if Iran doesn't accept an agreement to reopen the strait and roll back its nuclear programme.

Iran has mostly blocked the critical waterway for global energy since the US and Israel launched the war on Feb 28, causing a global spike in fuel prices and rattling world markets.

Meanwhile, a large oil slick has been detected in the Persian Gulf near Kharg Island, Iran's main crude oil export hub, raising fresh concerns over the condition of the country's oil infrastructure amid mounting regional tensions and shipping disruptions, according to a report by The New York Times.

Satellite imagery reviewed by the newspaper showed the slick spreading off the western coast of Kharg Island, a critical centre of Iran's oil export network. The spill had expanded to more than 20 square miles by Thursday, according to estimates from Orbital EOS, a global oil spill monitoring service cited by the news report.

Orbital EOS estimated that more than 3,000 barrels of oil may have been released into the waters of the Persian Gulf.

The exact cause of the spill remains unclear. However, the news report said Iran's oil and gas infrastructure has been under growing strain due to the ongoing US-imposed naval blockade linked to tensions around the Strait of Hormuz, one of the world's most strategically important oil transit chokepoints.