An oil slick stretching nearly the length of Yemen's Red Sea coast was spotted after a Houthi attack damaged a crude tanker, the Conflict and Environment Observatory said Wednesday.
Satellite imagery from the European Space Agency showed the slick on Tuesday near the location of the Houthi attack on the Chios Lion vessel, said CEOBS, a UK charity which monitors the environmental impact of conflict.
The apparent slick, measuring 220 kilometres (135 miles) long, suggested the "damaged vessel was releasing oil", it said on social media platform X.
The Liberia-flagged oil tanker Chios Lion was attacked 97 nautical miles northwest of the Yemeni port city of Hodeidah on Monday, according to maritime security agencies.
An uncrewed surface vessel "impacted" the tanker, resulting in minor damage, the United Kingdom Maritime Trade Operations reported.
CEOBS said the oil slick started 106 nautical miles northwest of Hodeidah, a location consistent with Monday's attack on the Chios Lion.
An image posted by the charity showed what it said was an oil slick in the Red Sea near the Farasan marine sanctuary off the coast of Yemen and Saudi Arabia.
On Tuesday the Joint Maritime Information Center, run by a Western naval coalition, said the Chios Lion was investigating a potential oil spill following the Houthi attack.
The Houthis have been attacking ships in the Red Sea and the Gulf of Aden since November in a campaign they say is intended to show solidarity with Palestinians amid Israel's war on Gaza.
In March, they sank a Belize-flagged, Lebanese-operated vessel carrying 21,000 tonnes of ammonium phosphate sulfate fertiliser on board.
The incident triggered concerns that leaking fuel and chemical pollutants could spill into the Red Sea, harming coral reefs and marine life.
"These ongoing strikes on various oil, chemical and cargo tankers not only put risks to maritime personnel and shipping traffic in general, but seriously deteriorating ecosystems in the Red Sea," said Wim Zwijnenburg of Dutch peace-building group PAX
"The current strikes are a further threat to the environment and coastal communities in Yemen," he told AFP.