Haze from fires in Indonesia blanketing Singapore could persist for weeks or longer, Prime Minister Lee Hsien Loong said on Thursday, as the smoke drove air quality to "hazardous" levels and disrupted business and travel in the region.
Illegal burning of forests and other land on Indonesia's Sumatra island to clear space for palm oil plantations is a chronic problem during the June to September dry season.
One Indonesian minister accused Singaporeans of acting like children, but pollution levels in the normally pristine city-state have shattered records set in 1997, raising diplomatic tensions and concerns about the economic impact.
"It can easily last for several weeks and quite possibly longer until the dry season ends in Sumatra," Lee told a news conference, warning of action if Singapore-linked companies were behind the burning. "On the scale of it, it's unlikely to be just small stakeholders slashing and burning."
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On the fourth day of heavy smog, the smell of burned wood filled the air, skyscrapers were barely visible and haze hung in the tunnels that link Singapore's metro stations and shopping malls in the central core. Some residents wore surgical masks or covered their faces with hankerchiefs when they walked outside.
Singapore will suffer "an immediate hit to tourism", investment bank Barclays Plc said, noting that retailers, hotels, restaurants, gaming and other tourism-related sectors make up about 5-6 percent of the city-state's economy.
"We think arrivals will recover quickly when the haze dissipates," it said in a report. "But the situation is fluid - prolonged hazardous conditions could affect Singapore's international reputation."
An Australian couple on holiday said they cancelled a visit to the zoo and would probably stay indoors.
"I'm never coming back to Singapore at this time of the year again," said the husband, who identified himself only as Rob.
Singapore, a major financial centre, sent officials to an emergency haze meeting in the Indonesian capital, Jakarta.
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"We will insist on definitive action," Environment and Water Resources Minister Vivian Balakrishnan said on his Facebook page. "No country or corporation has the right to pollute the air at the expense of Singaporeans' health and well-being."
As Singapore put pressure on Jakarta to act, the Indonesian minister leading the response efforts hit back.
"Singapore shouldn't be like children, in such a tizzy," Coordinating Minister for People's Welfare Agung Laksono told reporters, adding the government was investigating whether large companies were behind the fires.
"If there are, some are owned by Indonesians, Malaysians, Singaporeans," he said. "We will take action if they are found responsible. But there must be a process."
To identify the culprits, Singapore has provided satellite data to Indonesia and will publish high-resolution photographs of the hotspots with the geographical coordinates to help interest groups such as Greenpeace pinpoint the sites.