Satellite images showed the Persian Gulf spill covered more than 20 square miles by Thursday, with monitoring firm Orbital EOS estimating over 3,000 barrels had been released.
The cause was unclear, but concern centred on Iran's main crude export hub as a US-imposed naval blockade and stalled talks over the Strait of Hormuz strain storage and shipping.
Analysts said stranded tankers and crude stored offshore raise spill risks, while a rupture in the ageing pipeline linking Kharg Island to the Abuzar field was another possible source.
Was Iran's oil spill an accident from US pressure or a deliberate strategic move in the escalating conflict?
With war paralyzing international law, who is accountable for cleaning up the Persian Gulf's catastrophic oil spill?
Will the world prioritize environmental rescue for the Gulf or scramble to secure its own threatened energy supply?