An oil well was set alight in Iran's south-western province of Khuzestan on Tuesday before the blaze was brought under control, an oil company official said.
“One of the wells in the Shadegan field was set on fire by unidentified people this morning,” the head of the state-owned Marun Oil and Gas Production Company told state television.
“The fire was immediately brought under control,” said Ghobad Nasseri. He added that the damage was still being assessed.
The Shadegan field has a capacity of 110,000 barrels per day of crude, state television said.
There are about 20 active wells in the Shadegan field, which has an estimated total production capacity of about 70,000 barrels per day.
The oilfield is in the oil-rich south-western Khuzestan province, home to Iran's Arab minority. It has long been the scene of anti-government unrest.
Earlier this month, Iran reported an accidental explosion at the oil refinery in the province's third largest city Abadan, which caused damage but no casualties.
Industrial accidents are common in Iran, with some blaming US sanctions, which severely limit its ability to import spare parts for maintenance.
Iran has accused Israel of several attacks on facilities and scientists linked to its nuclear programme. Israel has neither denied nor confirmed the allegations.
Iran has the world's second-largest proven gas reserves and its fourth-largest oil reserves but exports have been heavily reduced by US sanctions.
Talks on restoring a 2015 nuclear deal with major powers, including with the US, had raised hopes of Iranian oil returning to world markets, but diplomats have expressed mounting pessimism in recent weeks.