By Thursday evening, the number of hotspots stood at 799 nationally, up from 372 a day earlier.
Most were in Central Kalimantan, a province on Borneo island that Indonesia shares with Malaysia and Brunei, followed by the south of Sumatra island.
“Central Kalimantan recorded the largest increase (in hotspots), so field operations are being strengthened,” said the statement.
The ministry expressed particular concern about an area around the Tanjung Puting National Park, an important habitat for endangered orangutans.
Water-bombing and cloud-seeding operations to make rain have been hampered by low visibility due to smoke from the fires, it added.
The ministry said several locations in Sumatra and Kalimantan were experiencing “unhealthy to very unhealthy conditions, even locally hazardous” due to the haze emitted by the blazes, turning the sky in some areas orange.
“If air conditions worsen, people are advised to reduce outdoor activities and wear masks when outside,” it said.
