JAKARTA - Air quality in Sumatra appears to have improved on Friday afternoon, but conditions in parts of Kalimantan remain 'hazardous' for much of the day.

Latest Pollutant Standards Index (PSI) readings from Indonesia's Meteorology, Climatology and Geophysics Agency (BMKG) showed that the Central Kalimantan capital of Palangkaraya peaked at 1,607 PSI at 8am before settling down at 587 PSI later at 2pm.

Pontianak, a city in West Kalimantan, clocked levels as low as 114 PSI in the morning, only to have it surge to 724 PSI by 2pm.

Banjarbaru in the south of Borneo Island, however, held steady under the moderate zone, from registering 26 PSI at midnight before rising to 67 PSI at 2pm.

Medan and Pekanbaru, both cities in Sumatra, saw significant improvements, recording 114 PSI and 170 PSI respectively as of 2pm Friday.

These readings come after the PSI in Kalimantan and Sumatra surge to alarming levels the previous day, offering no respite for people in the two regions observing the Muslim holiday of Hari Raya Haji on Thursday.

Parts of Indonesia, Singapore and Malaysia have been blanketed in a thick haze caused by the illegal burning of peatland and forests in Indonesia in recent weeks.

Fingers have been pointed at large plantation companies and their suppliers, who in turn blame small-time farmers and indigenous village folk for the fires.