Singapore's smog problem from forest fires in Indonesia worsened Wednesday as air pollutant levels reached a 16-year high.
Foreign tourists and convention delegates joined Singaporeans in complaining about the smoky haze enveloping the city-state of 5.3 million inhabitants, which welcomed 14.4 million visitors in 2012.
The Pollutant Standards Index soared to 172 at 3 pm (0700 GMT), well past the officially designated "unhealthy" threshold of 100, according to the National Environment Agency (NEA) website.
It was Singapore's worst haze reading since September 1997 when the number peaked at 226.
The reading rose to 155 on Monday night, overtaking the second highest reading of 150 recorded in 2006.
Southeast Asia's haze crisis in 1997-1998 caused widespread health problems and cost the regional economy billions of dollars as a result of business and air transport disruptions.
Zac Kot, 40, a business owner from the United States who was in Singapore for a holiday with his wife and two young girls, said they were cutting their visit short by two days.
"Has the haze affected us? Definitely. We are going to leave Singapore two days early because we are having trouble breathing," he told AFP.
"It's from a health standpoint, really."
Russian tourist Egor Podolsky, 23, said the haze forced his girlfriend and him to alter their travel itinerary in the city-state.
"You can see people wearing masks when walking around... It's not good, it's definitely not good," he told AFP.
Surgical masks flew off drugstores' shelves as residents and offices bought in bulk for their families and staff.
Singapore officials continued to take to social media to address Singaporeans' rising anger over the unabating haze conditions.
Foreign minister K. Shanmugam strongly rebutted netizens' criticism that the Singapore government was being soft on Indonesia.
"Every country is sovereign and we can't intervene in the actions in other countries," he said in a Facebook posting on Wednesday.
"The burning is taking place in Indonesia. What do you think Singapore can do about that?" he wrote.
Shanmugam and Singapore's environment minister Vivian Balakrishnan on Tuesday spoke with their Indonesian counterparts to emphasise "the urgency of the situation" and offer help to fight the fires in Sumatra, a government statement said.
On Monday, Indonesian forestry ministry official, Hadi Daryanto, shifted some of the blame to Malaysia and Singapore, saying their palm oil companies that had invested in Indonesia were also responsible.
Explore further: Haze returns to Malaysia