Jakarta – Some 20,000 people have reported respiratory illnesses in Riau as forest fires and the resulting haze continued to worsen on Monday, the local health agency reported.

"That is the data we've compiled from a number of districts and municipalities since late January to Sunday [Feb. 23]," Zainal Arifin, the head of the Riau Health Agency, said in Pekanbaru on Monday.

Last month, fewer than 5,000 people reported respiratory problems in Riau. Last week, however, the figure jumped to 15,000 before surpassing 20,000 on Sunday, the health authority reported.

"We've been focusing only on patients with respiratory problems because they are the focus of the Ministry of Health," he told Indonesian news portal Bisnis Indonesia.

Zainal urged people in Riau to minimize their time outdoors, citing the poor air quality, especially in the town of Dumai and in the Pelalawan and Siak districts. "Toddlers and people with asthma should avoid outdoor activities," he said. "Workers should wear masks in anticipation of respiratory illnesses."

Officials with Sultan Syarif Kasim II Airport in Pekanbaru said at least 12 flights were delayed, canceled or rerouted because the haze had reduced visibility in the province.

"Between 5 a.m. and 9:30 a.m. [on Monday], the visibility was only 500 meters," airport manager Baekuni said on Monday. "The minimum visibility for safe flights is at least 1,000 meters."

Affected routes included those to and from Malaysia and Singapore, as well as Bandung, Batam, Jakarta and Medan, on flights operated by Aviastar, Citilink, Garuda Indonesia, Lion Air and Tigerair Mandala. A Citilink flight from Jakarta, which was supposed to land at Pekanbaru airport at 7:20 a.m., was diverted to Batam.

Forests in Riau began burning again earlier this month, with officials blaming local farmers for using the slash-and-burn method to clear land. On Monday, the Meteorology, Climatology and Geophysics Agency (BMKG) said 1,398 hotspots were detected across Sumatra, with most of them concentrated in Riau.

Ahmad Agus Widodo, an analyst with the Pekanbaru office of the BMKG, said Bangka-Belitung and Lampung each reported one hotspot. South Sumatra reported two, Aceh five, Jambi 24, Riau Islands 43 and North Sumatra 85.

"Most hotspots were recorded in Riau province," Ahmad told liputan6.com. "[NASA's] Terra and Aqua satellites detected 1,234 fire hotspots across eight districts and municipalities in Riau."

He added the figure marked a significant rise from the roughly 80 hotspots detected in Riau on Sunday. Ahmad said that with the wind blowing toward the south, haze was spreading to the neighboring provinces of Jambi and West Sumatra.