Satellites have detected 17 hot spots from forest and land fires in Indonesia's Riau province on Friday (Aug 26), more than double the number overnight, as strong winds send acrid smoke north-east towards Singapore.

The National Space and Aviation Agency of Indonesia (Lapan) satellites detected only seven hot spots in the province the day before, Indonesia's disaster management agency spokesman Sutopo Purwo Nugroho said.

The fire-control task force on the field, however, reported 67 hot spots, with 44 concentrated in the Rokan Hilir district, he said, adding: "Dense smoke was billowing from the hot spots."

Separately, Mr Sutopo told The Straits Times that dry conditions, sporadic rains, and common incidents of illegal land clearing by burning in the past week were causing the spike in the number of hot spots.

"The wind is carrying the smoke from forest and land fires in Riau north-east to Singapore. The concentration of smoke observed is still quite thin," he added.

The typical wind pattern during the dry season in Riau had "always been feared" to bring the smoke from the province to Singapore, as had occurred in 2013, 2014 and 2015, he said.

Meanwhile, Mr Sugarin, head of the Pekanbaru branch of the meteorology, climatology and geophysics agency, told The Straits Times the wind pattern is unlikely to change during the dry season, which peaks in September.

He added that the wind is also blowing strongly at 10 to 15 knots, but that air quality and visibility are "still good".

"With hot and dry conditions coupled with strong winds, fires can spread easily," he said.

However, he said the fires are still under control and the "haze will not be bad like last year".

Millions of people in South-east Asia were affected by thick smoke from fires that covered many parts of the region in the second half of last year.

The crisis almost brought Indonesia to the brink of a national emergency.