Indonesia has shot back at claims the country is solely responsible for the fires that have created a thick haze across parts of Malaysia this week and forced the closure of hundreds of schools.

“The Indonesian government has been systematically trying to resolve this to the best of its ability. Not all smog is from Indonesia,” said Indonesia’s environment minister, Siti Nurbaya Bakar, in a statement on Wednesday, in a rebuke of its neighbour.

Siti Nurbaya accused Malaysia of a lack of transparency, saying the smog affecting Malaysia could have originated from Sarawak, peninsular Malaysia or Indonesian Borneo. “The Malaysian government should explain this objectively,” she said.

On Wednesday, Malaysia’s environment and climate change minister, Yeo Bee Yin, wrote on Facebook: “Let the data speak for itself. Minister Siti Nurbaya should not be in denial.”

In the post Yeo included data from the ASEAN Specialised Meteorological Centre (ASMC), which showed the total number of hotspots in Kalimantan was 474, with 387 in Sumatra. By comparison, only seven were recorded in Malaysia.

Indonesia’s Disaster Mitigation Agency said more than 3,600 fires had been detected on the islands of Sumatra and Borneo by weather satellites, leading to very poor air quality in six provinces with a combined population of more than 23 million.

On Friday, Malaysia sent a diplomatic note urging Indonesia to take immediate action to address the fires. Malaysia has shut more than 400 schools in the eastern state of Sarawak and sent half a million face masks to the area to combat poor air quality.

Map showing hotspot activities in Sumatra and Kalimantan which are likely to continue under the prevailing dry conditions. Photograph: Asean Specialised Meteorological Centre

Indonesia has claimed the smog affecting Malaysia and other areas in south-east Asia, is also from fires across the region, including in peninsular Malaysia and Vietnam.

Tiny particles in the haze pose several health risks, including stroke, cardiovascular disease and respiratory infections.

Scientists say that exposure to smoke from the forest fires could lead to 36,000 premature deaths a year on average across Indonesia, Singapore and Malaysia over the next few decades if trends continue.

Malaysia’s ambassador to Indonesia, Zainal Abidin Bakar, attempted to smooth over the recent barbs, telling reporters on Wednesday night that Malaysia was not engaging in a blame game, but offering assistance to help tackle the fires.