Singapore called on Thursday for "definitive action" from Indonesia as air quality stuck at very unhealthy levels for a second day because of forest fires in its neighbour, disrupting businesses in the prosperous city-state.
Work at several Singapore construction sites slowed with few workers seen outdoors and fast-food operator McDonald's suspended its delivery service. The Singapore military suspended outdoor training.
"No country or corporation has the right to pollute the air at the expense of Singaporeans' health and wellbeing," Singapore's Environment and Water Resources Minister Vivian Balakrishnan said on his Facebook page.
The chief of Singapore's National Environment Agency, Andrew Tan, was heading to an emergency haze meeting convened in the Indonesian capital, Jakarta, he said.
"We will insist on definitive action."
The illegal burning of forest on Indonesia's Sumatra island, to the west of Singapore, to clear land for palm oil plantations is a chronic problem, particularly during the June to September dry season.
Singapore, which prides itself on its clean environment and usually enjoys clear skies, saw its air quality deteriorate to unhealthy levels on Monday.
A pollution standards index (PSI) soared to a record high of 321 on Wednesday night, indicating air quality had deteriorated to "hazardous levels".
The indicator later eased to 153, although visibility appeared worse than it was on Wednesday when the readings were higher. Singapore's apartment blocks were shrouded in a haze on Thursday and the skyline was obscured.
A PSI reading above 300 indicates "hazardous" air quality, while a reading between 201 and 300 means "very unhealthy".
The 321 level is above the previous 226 record reached in Singapore in 1997 when smog from Indonesian fires disrupted shipping and air travel across Southeast Asia.
Operations at Singapore's Changi Airport, a major Asian aviation hub, have not been affected this time.
The haze from Indonesia has also shrouded parts of Malaysia.
Singapore's drug stores and supermarkets have run out of face masks and residents have taken to social media to complain about their giant neighbours and about the ineffectiveness of the Association of Southeast Asian Nations (ASEAN) regional grouping to do anything.
"ASEAN and its policy of non-interference in this matter of severe transnational air pollution is akin to the police catching an arsonist red-handed and letting him go scot-free," said Peh Sik Wee, chief strategic officer at Aidos Global, a consultancy.
Indonesian officials have tried to deflect blame by suggesting companies based in Singapore may be partly to blame for the blazes. Singapore has said it wants Indonesia to provide maps of land concessions so it can act against firms that allow slash-and-burn land clearing.
"What we know is that there are several foreign investors from Singapore involved," said Hadi Daryanto, a senior official at Indonesia's Forestry Ministry.
"But we can't just blame them for this since we still need to investigate this."
Singapore-based palm oil companies with land concessions in Indonesia include Wilmar International Ltd, Golden Agri-Resources Ltd and First Resources Ltd.
All three said on Wednesday they had "zero burning" policies and used only mechanical means to clear land.
Cargill, whose Asia-Pacific regional hub is in Singapore, said there were no fires on its plantations in South Sumatra and West Kalimantan.