JAKARTA, Indonesia (AP) — Indonesia denied Friday that forest and peat fires on Sumatra and Borneo islands were causing the haze in Malaysia, after the neighboring government sent a letter complaining about the air quality and asking to work together to deal with the fires.

Forest and peat fires are an annual problem in Indonesia that strains relations with neighboring countries. In recent years, smoke from the fires has blanketed parts of Indonesia, Singapore, Malaysia and southern Thailand.

Some parts of Malaysia said they experienced smoke from the Indonesian fires since last week, but the Indonesian government denied its fires are the cause.

“Until now there is no transboundary haze. No cross-border smoke. I don’t know what basis Malaysia uses to make these statements,” Siti Nurbaya Bakar, Indonesian Environment and Forestry minister, told The Associated Press.

Malaysia’s capital, Kuala Lumpur, and Kuching, one of its cities on Borneo island, were recently ranked as among the world’s top five most polluted cities by IQAir, a Swiss air quality technology company.

There are more than 1,900 recorded hotspots on Sumatra, mostly in South Sumatra province, according to the data from Indonesia’s Meteorology, Climatology and Geophysics Agency. On Monday, the local government in South Sumatra asked residents to work from home and schools to go online amid a blanket of haze. Hundreds of forest fires in South Kalimantan province in Borneo island made the smoke haze even more widespread, especially during the last week. The local government has also called the students to do online learning as the air quality is unhealthy.

Indonesian authorities have so far ignored Malaysia’s request.

Bakar provided government data showing that, while it fluctuates, air quality in the regions where the peat and forest fires were found in the past week were getting better.

“We are still working to handle the forest and land fires in Borneo and Sumatra islands as well as possible. And the picture of the situation on the ground is getting better,” she said, adding that rain was aiding the process in multiple areas, including through government rain-seeding efforts.