Singaporean Prime Minister Lee Hsien Loong has warned that smog engulfing the city could last for weeks and urged people to stay indoors.
At 13:00 local time on Thursday, the standards index of the pollution has reached 371, which is said to be way above hazardous.
The high-level record-breaking pollution is caused by illegal forest fires in Indonesia's Sumatra Island, according to the BBC News.
The Singaporean prime minister said that smog could "easily last for several weeks and quite possibly longer until the dry season ends in Sumatra", while urging its people to "stay indoors where possible and avoid heavy outdoor activities".
The two neighbors are blaming each other for the smog and an emergency environmental meeting is taking place on Thursday in the Indonesian capital city Jakarta.
Earlier, Singaporean Environment and Water Resources Minister Vivian Balakrishnan updated his Facebook status saying he would demand "definitive action" from the Indonesia government.
"No country or corporation has the right to pollute the air at the expense of Singaporeans' health and wellbeing," said Vivian Balakrishnan.
Responding to the accusations from the Singaporean officials, the Indonesian Minister for People's Welfare Agung Laksono said that Singapore was "behaving like a child".
"This is not what the Indonesian nation wants, it is because of nature," said Agung Laksono.
Parts of Malaysia have also been affected by the forest fires and more than 200 schools in the hazardous areas have been ordered to close down for some time.
Buildings in Singapore have been obscured by the smog and the smell of burnt wood in the city has forced many people to rush for disposable face masks. The administration has said that it will constantly update on the pollution levels.
Road and air transport has been affected.
