Indian Oil Corp, the country's biggest oil refiner, will fully shut its 160,000 barrels per day (bpd) Mathura refinery in northern India from Sept. 21 for a three-week maintenance, a source familiar with the plan said on Monday.

The company will shut its sole crude unit at the plant for maintenance, rendering other units idle, the source, who did not wish to be named, told Reuters.

IOC also plans to shut a hydro cracker and a crude unit at its 274,000 bpd Koyali refinery in eastern Gujarat state from Sept. 5, the source added.

A crude unit of about 44,000 bpd would be shut for maintenance for 25 days while the hydro cracker unit would be shut for about 15 days, the source said.

A hydro cracker unit produces middle distillate fuels like diesel, kerosene and jet fuel.

IOC has a capacity to process 1.294 million bpd oil from its 10 refineries.

An IOC spokesman for refineries could not be reached for comments.