Indonesian satellites detected 17 hot spots from forest and land fires in Riau province yesterday, more than double the number overnight, as strong winds sent acrid smoke north-east towards Singapore.

Seven hot spots were detected by the satellites belonging to the National Space and Aviation Agency of Indonesia (Lapan) on Thursday, said Indonesia's disaster management agency spokesman Sutopo Purwo Nugroho.

But the fire-control task force on the ground reported 67 hot spots, with 44 in the Rokan Hilir district, Mr Sutopo said.

"Dense smoke was billowing from the hot spots," he added.

Separately, Mr Sutopo told The Straits Times a combination of dry conditions, sporadic rains and common incidents of illegal land clearing by burning in the past week has caused the spike in 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.

This typical wind pattern during the dry season in Riau is responsible for blowing smoke from the province towards Singapore, as happened in 2013, 2014 and 2015, said Mr Sutopo.

Meanwhile, Mr Sugarin, head of the Pekanbaru branch of the meteorology, climatology and geophysics agency, told The Straits Times yesterday that the wind pattern is unlikely to change during the dry season, which hits a peak next month. "With hot and dry conditions coupled with strong winds, fires can spread easily," said Mr Sugarin, who goes by one name.

However, he said the fires are still under control and the "haze will not be bad like last year". The number of hot spots hit 14,451 in August last year.

Some 7,200 firefighters have been deployed in Riau, together with six aircraft for waterbombing and cloud-seeding, Mr Sutopo said. Thousands of canals, reservoirs and wells have also been built to keep the ground moist and help prevent the fires from spreading.

Ms Lee Chen Chen, director of policy programmes at the Singapore Institute of International Affairs, which has a team of researchers in Riau currently, said their local sources told them the fires in Northern Riau are not in plantations.

"Since the fires are not on concession lands, we believe it is important for the local government to take a central role to suppress the fires quickly with the help of companies," she said.

Last year's haze crisis, which affected millions in Indonesia as well as neighbouring Singapore and Malaysia, almost brought Indonesia to the brink of a national emergency.

To prevent a repeat, President Joko Widodo has ordered the Indonesian authorities to clamp down on errant farmers and companies, while beefing up fire-fighting resources in high-risk areas.

Since January, police have nabbed 454 individuals and a number of people linked to nine companies suspected to have "started the fires".