Haze blankets Singapore

A tourist poses for photos with the Merlion (unseen) in the hazy skyline of Singapore June 20, 2013. Singapore's haze deteriorated to "hazardous" levels late on Wednesday as smoke from slash-and-burn land clearing in Indonesia enveloped the city-state, inflaming tensions between the Southeast Asian neighbours. The Pollution Standards Index (PSI) soared to a record high of 321 at 10 p.m., up from 290 just an hour earlier and below 200 earlier in the day. A PSI reading above 300 indicates "hazardous" air quality, while a reading between 201 and 300 means "very unhealthy". REUTERS/Edgar Su

Commuters cover their mouths as they wait to cross a road in the haze in Singapore June 20, 2013. REUTERS/Edgar Su

Motorists travel through haze in Pekanbaru, Indonesia's Riau province June 20, 2013. REUTERS/Beawiharta

A woman takes photos of the hazy skyline of Singapore June 19, 2013. REUTERS/Edgar Su

Office workers pass the hazy skyline of Singapore June 19, 2013. REUTERS/Edgar Su

Malaysia's landmarks (from L-R) Wawasan Bridge, Millennium Monument, Putra Mosque and the office of prime minister Putra Perdana are shrouded with haze in Putrajaya June 18, 2013. REUTERS/Bazuki Muhammad

Children cover their noses near burnt land in Marpoyan Damai sub district, in the outskirts of Pekanbaru, in Indonesia's Riau province June 20, 2013. REUTERS/Azwar

Firefighters spray water on the burning land in Marpoyan Damai sub district, in the outskirts of Pekanbaru, in Indonesia's Riau province June 20, 2013. REUTERS/Azwar

A resident tries to extinguish fire on the outskirt of Pekanbaru in Indonesia's Riau province June 19, 2013. REUTERS/Azwar

A woman and a child, wearing face masks, ride a motorbike through haze in Pekanbaru, the capital city of Riau province June 20, 2013. REUTERS/Beawiharta

Construction workers wear face masks, to protect them from a heavy smoke haze, as they perform morning exercises at the start of their shift in Singapore June 20, 2013. REUTERS/Tim Wimborne

Construction workers wear face masks, to protect them from a heavy smoke haze, as they perform morning exercises at the start of their shift in Singapore June 20, 2013. REUTERS/Tim Wimborne

Waitress Geraldine Ontong, from the Philippines, wearing a face mask serves customer at a pub in Singapore's central business district June 20, 2013. REUTERS/Edgar Su

An office worker wearing a face mask rests in a park in Singapore's central business district June 20, 2013. REUTERS/Edgar Su

A man sells N95 safety face masks to office workers for S$10 ($7.80) a piece in Singapore's central business district June 20, 2013. REUTERS/Edgar Su

Students, one wearing a face mask and the other covering her mouth with her headscarf, leave for home after an early dismissal from school due to the haze in Muar, in Malaysia's southern state of Johor bordering Singapore, June 20, 2013. REUTERS/Bazuki Muhammad

An aerial view of haze covering Indonesia's Riau province June 20, 2013. REUTERS/Beawiharta

A man rides past the hazy skyline of Tanjong Rhu residential area in Singapore June 17, 2013. REUTERS/Edgar Su

A hotel guest rests in the pool of the Marina Bay Sands Skypark in front of the hazy skyline of Singapore June 17, 2013. REUTERS/Edgar Su

Partygoers line up to enter a nightclub at Marina Bay Sands, as haze shrouds the skyline of Singapore in the background, late June 19, 2013. REUTERS/Tim Chong