Dozens of critically endangered orangutans saved from rampant wildfires in Indonesia

Dozens of critically endangered orangutans have been rescued in recent weeks from rampant wildfires burning across Indonesia that have cloaked the region in toxic haze, conservation groups said.

Singapore experienced the longest duration of unhealthy air levels since Southeast Asia's most severe haze crisis hit in 2015, officials told AFP.

The fires have triggered a months-long pollution spell that has closed schools, fuelled a surge in respiratory conditions both among humans and animals and restricted outdoor activities in Indonesia, Malaysia, Singapore and East Timor.

Read moreMonths-long Indonesia wildfires spew toxic haze across Southeast Asia

Pollution levels ranged from unhealthy to very unhealthy across the region on Sunday, as fires continued to burn and emit smoke on Borneo and Sumatra islands, intensified by a turbo-charged El Nino weather phenomenon.

Swiss-based air quality monitor IQAir again ranked Singapore and Kuala Lumpur among the world's top five most polluted major cities on Sunday afternoon.

Singapore has now seen "the longest duration of air quality being in the unhealthy range since 2015", said Jason Evans Tan, a deputy director at Singapore's National Environment Agency, noting the current spell began on October 5.

In Indonesia, groups are working to save wildlife, including orangutans, from the fires.

On Saturday, the West Kalimantan conservation agency and Indonesian non-profit YIARI said a team evacuated 51 orangutans from locations in the province from August 6 to October 19.

And figures from Indonesia's forestry ministry suggested this week that the number rescued over recent months in Kalimantan could be as high as 96.

Officials could not be immediately reached to clarify the number.

On Saturday, three conservation agencies saved a 20-year-old male orangutan in Hampangen village in Central Kalimantan on Borneo island.

"The evacuation process was carried out with great caution," the agencies said.

"After the orangutan was sedated, the medical team immediately conducted a health examination before taking the animal to the... rehabilitation centre," it said.

"We tried to check and found that there are a few orangutans left in these small forest patches," WWF Indonesia conservation coordinator Fenky Wirada said.

Indonesia's transport ministry also said around 2,400 flights across the country have been affected by the haze since mid-August.

"Haze reduces visibility around airports, which can lead to delays, disruptions, and even flight cancellations," the ministry said.

Indonesia's forest fires spark public health crisis across Southeast Asia

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'Not enough rain' 

In Singapore, concentrations of PM2.5, a fine particulate pollutant, remained elevated in western parts on Sunday, with the 24-hour Pollutant Standards Index straying in the "very unhealthy" range at times.

Although PM2.5 is the dominant pollutant during haze episodes and one of six indicators used to calculate Singapore's overall PSI, it is not the same as the PSI itself.

Wang Jingyu, a Singapore-based atmospheric sciences expert, said the region was firmly in the grip of a super El Nino weather phenomenon.

Because "of the super El Nino across the entire Southeast Asia, the sea surface temperature is cooler than normal", said Wang, an assistant professor at Singapore's Nanyang Technological University.

"Under these conditions, cooler sea surface temperature means we do not have enough evaporation from the ocean," meaning insufficient rain, he told AFP.

"We do not have enough rain. The fire cannot be easily put out."

Dry conditions were exacerbated by a high number of typhoon systems elsewhere in eastern Asia, Wang said.

Typhoons "absorbed moisture like a sponge" deflecting it away from the regions where the fires were burning, Wang said.