Four oil storage tanks are in flames at the Balongan refinery in West Java, owned by state oil company Pertamina, after an explosion on Monday morning.

“The tanks are now in water isolation so the blaze will not spread to other tanks,” said National Police’s spokesman Ahmad Ramadhan during a briefing on Tuesday.

About a thousand locals have been evacuated from the area.

The cause of the fire was not clear, but the company said the blaze broke out during a lightning storm.

The local disaster agency said one person had died from a heart attack after the explosion.

Six severely wounded people have been hospitalised in the capital Jakarta, about 200km from the sprawling plant, which opened in the mid-90s and can refine some 125,000 barrels of oil a day.

At least 30 others sustained minor injuries.

Pertamina has insisted the fire is not likely to cause fuel supply disruptions due to a high volume of stock.