Indonesian President Susilo Bambang Yudhoyono has apologised to Singapore and Malaysia over fires that have cloaked the countries in thick haze, as thousands more emergency workers were deployed on Tuesday to tackle the blazes.
Southeast Asia's worst smog crisis for years pushed haze levels in Singapore to a record high last week, with residential buildings and skyscrapers shrouded and daily life for millions in the city-state dramatically affected.
The smog has drifted north and is now badly affecting Malaysia, while in a badly-hit province on Indonesia's Sumatra island—where the fires are raging in peatland—hundreds gathered to pray for rain.
The crisis has triggered a war of words between Jakarta and its neighbours, with an Indonesian minister accusing Singapore of acting "like a child". But Yudhoyono sought to ease tensions by issuing a public apology late Monday.
"As the president of Indonesia, I apologise for what has happened and ask for the understanding of the people of Malaysia and Singapore," he said. "We accept it is our responsibility to tackle the problem."
Singapore has repeatedly demanded that Indonesia step up action to tackle the blazes, but Jakarta has hit back, saying palm oil companies from Singapore and Malaysia which run plantations on Sumatra also share the blame.
Smog from Sumatra is a recurring problem during the June-September dry season, when big companies and smallholders alike light fires to clear land, in a cheap but illegal method of clearing space for planting.
Southeast Asia suffered its worst smog outbreak in 1997-98 and was hit with a serious recurrence in 2006.
Indonesia's national disaster agency said Tuesday that more than 3,000 emergency workers, including police and soldiers, would be sent over the next two days to Riau province, where the fires are centred.
There are already about 2,300 personnel on the ground tackling the blazes and providing support to those affected, said agency head Syamsul Ma'arif.
They are being backed by helicopters and planes dropping water and attempting to chemically induce rain through cloud-seeding.
But agency official Agus Wibowo told AFP from Riau that airborne efforts to fight the blazes were proving ineffective, so the agency was shifting its focus to "sending more men to the affected areas to fight the blazes on land".
"We are working very hard," he said.
Firefighters are having to resort to sticking hoses deep into the ground to tackle the fires burning under the surface of the carbon-rich peat, which is a time-consuming process.
While the smog has lifted from Singapore, which was enjoying its third straight sunny day on Tuesday after the air pollution index eased from the all-time highs of last week, Malaysia is now bearing the brunt of the crisis.
Air quality was "hazardous" for the second straight day in the country's busiest port, Port Klang on the Strait of Malacca facing Sumatra, with the air pollution index spiking to 487.
Five other districts, mostly in central Malaysia near the capital Kuala Lumpur, logged "very unhealthy" air quality.
Hundreds of schools that were forced to close in recent days reopened, but education officials advised against outdoor activities.
In Dumai city in Riau, where visibility has deteriorated to just 150 to 200 metres (500 feet to 650 feet) and residents have been advised to limit outdoor activities, hundreds gathered to perform special prayers calling for rain.
"This morning, we prayed to God for rain and for the efforts to fight the haze to be successful," said local environment official Basri, who like many Indonesians goes by one name.
Explore further: Obama says 'no greater threat to planet than climate change'