According to the National Iranian Oil Refining & Distribution Company (NIORDC) website, the refinery's director, Alireza Amin, said overhaul of five operation units of the facility began last month and wrapped up in less than one month.

He said overhaul operations had completed successfully without any incidents, and the refinery was operating at full capacity.

Located in the central city of Arak, the facility's Euro-4 petrol output has increased from 8 to 12 million liters per day to 16.5 million liters, he added.

Amin said that the overhaul of the refinery's distillation, liquid gas, catalytic reforming, visbreaker and kerosene purification units took 27, 19, 21, and 26 days, respectively, which was unprecedented in some units.

Imam Khomeini Shazand Refinery's last overhaul was in 2013, he said, adding overhaul of 4 or 6 other units of the refinery will be carried out this Iranian calendar year which began on March 21.