Satellite images reveal massive oil spill near Iran's Kharg Island

Satellite imagery has revealed a large oil spill spreading across dozens of square kilometers of sea near Iran's Kharg Island, the country's primary crude export terminal, as the US naval blockade continues to choke Tehran's oil trade and push its storage capacity toward its limits.

Images captured on May 6 by the European Space Agency's Copernicus Sentinel-2 program show a dark slick west of Kharg Island, which handles roughly 90% of Iran's oil shipments.

Reuters reported the suspected spill on Thursday, describing it as covering "dozens of square kilometres" near the island. Other reports estimate the affected area at more than 120 square kilometers.

Also Read: What is Kharg Island and why did the US target Iran's key oil hub?

The cause remains unclear. Analysts have raised possibilities including damage linked to military activity, emergency discharge operations due to mounting storage pressure, or leaks from offshore pipelines and tankers operating in conflict zones.

No official environmental assessment has been released by Iranian authorities.

The spill comes as Iran's onshore oil storage approaches critical capacity under the US naval blockade imposed on April 13. Iran's maximum onshore storage capacity is estimated at 42 to 50 million barrels, and approximately 60% was already in use before the blockade began.

US Treasury Secretary Scott Bessent warned in recent weeks that Kharg Island is "soon nearing capacity".

Fortune reported on May 1 that Tehran had begun proactively reducing crude output to stay ahead of capacity limits, with officials estimating a narrowing window of roughly one month before storage runs out entirely.

Also Read: Kharg Island explained: Why Iran's key oil hub matters

Iran has also mobilized a decommissioned tanker to load crude at Kharg, a sign of growing desperation. Al Jazeera reported that analysts at Kpler estimated Iran could deplete its crude storage within 12 to 22 days if the blockade persists.

Environmental toll mounts

The Kharg Island spill adds to a growing environmental crisis in the Persian Gulf. CNN reported in April that numerous oil spills had already become visible from space following strikes on oil facilities and ships by Iranian and US-Israeli forces since the war began in late February.

Experts have warned that leaked oil threatens the livelihoods of coastal populations, marine ecosystems including turtles and dolphins, and desalination plants that provide clean water to nearly 100 million people in the region.

Also Read: Kharg island invasion: The risks of a new US-Iran War

The same waters carrying roughly a fifth of global oil and gas flows "are now stained with oil slicks visible from space" -- an outcome that compounds the economic damage of a conflict already driving oil prices near $100 a barrel.