SINGAPORE –

Singapore will close its elementary and secondary schools on Friday as the haze from Indonesian forest fires pushed air quality into the "hazardous" range for the first time this year, covering the city-state with a layer of smog.

The three-hour pollutant standards index hit 320 as of 1 a.m. Singapore time, according to National Environment Agency, the highest level this year. A reading exceeding 300 is classified as "hazardous," where the public is advised to minimize outdoor activities.

A nationwide music test has also been postponed until Tuesday, the Ministry of Education said. Some international schools including the Swiss School in Singapore will also be shut on Friday. Junior colleges and universities will remain open.

"The 24-hr pollutant standards index for the next 24 hours is expected to be in the 'very unhealthy' range, and the possibility of the air quality going into the 'hazardous' range cannot be excluded," the environment agency said on Thursday.

The smog also led the city-state to cancel outdoor events in the past month and flights were diverted across Southeast Asia. Indonesia's enforcement of its laws against plantation owners is key to resolving the haze that covered parts of Southeast Asia in the past few weeks, Singapore Environment Minister Vivian Balakrishnan said last week.

"This is the first time I'm experiencing the haze first-hand. Today it really has worsened, you feel that," said Gokulnath Durai as he walked along the Singapore River wearing a face mask, which the tourist from Chennai, India, said was "a precautionary measure."

Singapore will also distribute N95 masks to "vulnerable and needy" citizens and permanent residents across 108 community clubs on Friday, the environment agency said.

Indonesia last week set a 14-day deadline to extinguish fires in Riau, and a 30-day target for South Sumatra and Jambi. The government has detained suspects in companies in various parts of the country.

"This haze is a rather sad thing," said Hungarian tourist Gabor Albert, who is visiting the city with his wife Katalin for three days. "We heard that this haze has been going on for a couple of years and that it always lasts six to seven weeks."