Indonesia’s president, Joko Widodo, arrived in South Sumatra on Thursday, pledging to tackle the raging forest fires that have engulfed the country and its neighbours in thick smog for almost three months.

Widodo, who cut short a visit to the White House [1] to deal with the crisis, will stay in the fire-hit region for the next few days, his officials said. The regencies of Ogan Komering Ilir (OKI) and Musi Banyuwasin in south Sumatra are among the worst-affected areas, with visibility in some places reduced to less than 50m.

“The president will work from the OKI regent office for a few days,” said the president’s spokesman, Ari Dwipayana, who said Widodo would focus on more effective responses to the out-of-control fires, as well as the emergency and medical response to the haze.

Indonesia’s social minister, Khofifah Indar Parawansa, confirmed on Wednesday the death toll from the effects of the haze had risen to 19 [2]. An estimated half a million people have suffered respiratory illnesses since the fires started in July.

More than 117,000 forest fires have been detected via satellite in Indonesia this year, most of which are believed to have been started deliberately to clear land for farming. The majority are on the islands of Sumatra and the Indonesian part of Borneo, known locally as Kalimantan.

Widodo’s visit came on the day a Bloomberg analysis said Indonesia had overtaken China and the US to become the world’s biggest climate polluter [3].

Typically, according to figures from the World Resources Institute, Indonesia emits 2.1 megatons of carbon dioxide a day (the US emits almost 16 megatons, and China 29.3). But Bloomberg calculated that the daily average emissions for Indonesia in September, as fires raged, were 22.5 megatons, rising to 23 megatons between 1-28 October. On 14 October, emissions from the fires alone soared to 61 megatons, almost 97% of the country’s total emissions.

Rain on Wednesday dampened fire hotspots in Sumatra and Kalimantan, but the air pollution index has remained high. The Indonesian Red Cross said it had dispensed 700,000 masks to people affected by the smog.

Widodo’s handling of the environmental crisis has been criticised, with thousands of university students demonstrating in Pekanbaru, South Sumatra, on Wednesday, calling on the government to ramp up its efforts to battle the haze, and to prosecute those behind the land-clearing blazes.

Seven people were arrested in September in connection with illegal burning [4], but Luhut Pandjaitan – a minister who has accompanied Widodo to South Sumatra – said this week that “economic considerations” meant the government would not name the corporations suspected of involvement in starting the fires [5].

Demand for palm oil – Indonesia is the world’s largest producer – means fires are routinely intentionally lit to clear the land. But a prolonged dry spell, combined with the El Niño drought, have exacerbated this year’s fires, with neighbouring Singapore and Malaysia also badly affected by the resulting haze.

The fires are calculated to have so far cost the Indonesian government more than US$30bn.

Claire Phipps in Sydney