The United Arab Emirates reported an oil spill from a tanker off its coast on Friday, as vessels in Gulf waters come under attack during the Middle East war.
Frequent attacks on ships have been reported in recent weeks near the Strait of Hormuz, at the heart of the conflict between Iran and the United States.
The authorities "detected a tanker oil spill affecting Umm Al Quwain's beaches", the Ministry of Climate Change and Environment said in a statement, referring to an emirate north of Dubai.
It said "teams immediately began containment, cordoning, clean-up and remediation... to limit environmental impacts", adding that the emirate's beaches had been closed.
Access to the area in Umm Al Quwain was restricted by police, AFP journalists who went there said.
The neighbouring emirate of Sharjah also closed one beach, Al Hamriyah, "as a proactive precautionary measure", the local government said.
Satellite images analysed by AFP showed a hydrocarbon slick on 19 October surrounding a vessel, likely the tanker GEM NO 2, located about 20 kilometres (12 miles) off the coast of Umm Al Quwain.
Images from 21 October, analysed by Wim Zwijnenburg from Dutch NGO PAX, revealed a slick about 40 kilometres long and covering an area of 190 square kilometres, stretching to just six kilometres from shore.
The British maritime security agency UKMTO reported on 9 October that a vessel had been hit by a projectile off the UAE coast, causing a fire that was later brought under control.
Maritime security company Vanguard also identified the vessel as the oil tanker GEM NO.2, sailing under a Panamanian flag.
Owned by Taiwan's Global Energy Maritime, the ship loaded 2 million barrels of oil in early March from a Saudi port.
Since then, it has been regularly transferring cargo with other ships along the Emirati and Omani coasts near the Strait of Hormuz, according to tracking data from maritime company Kpler.
The images do not make it possible to determine whether it is thick crude oil or "a thin light oil sheen", Zwijnenburg said.
"If it is crude oil, then it is a serious pollution risk as this will end up on the beaches, affect marine ecosystems, including birds and turtles that can get stuck," he said.
"If it is a light oil sheen and mostly diluted oil, the hope is that it evaporates fast, and (you) only have short-term risks," Zwijnenburg added.
Foul odours
Many residents in the north of the country have reported chemical smells on social media in recent days, including residents in northern districts of Dubai, the largest city in the UAE.
"For the past two days it smelled like 10 gas stations spilled their gas everywhere," a Sharjah resident told AFP, asking to remain anonymous.
"I was on my balcony and panicked thinking gas was leaking in my house and I will blow up everyone."
The UAE says the odours "pose no health risks to residents".
Beyond efforts to contain the oil spill, "monitoring and assessing its environmental impact will also be essential to protecting marine ecosystems and the communities that depend on them," Inesaf Benzaki, campaigns lead at Greenpeace MENA, told AFP.
Since the start of the Middle East war in February with US-Israeli strikes on Iran, Tehran has claimed control over the Strait of Hormuz and regularly targets ships that transit there without its authorisation.
Washington, in response, has imposed a blockade on Iranian ports and escorts tankers through the passageway.