Singapore is urging people to remain indoors amid unprecedented levels of air pollution after a smoky haze wrought by forest fires in neighboring Indonesia worsened dramatically. Nearby Malaysia has closed 200 schools.

Singapore's main measure for air pollution surged to an all-time high Thursday afternoon and breached a "hazardous" classification that can aggravate respiratory ailments.

Business and flights have not been disrupted, but the smog has strained diplomatic ties between Singapore and Indonesia. Officials in the city-state say Jakarta must do more to halt fires on Sumatra island started by plantation owners and farmers to clear land cheaply.

Singapore's Environment Minister Vivian Balakrishnan said Thursday that "no country or corporation has the right to pollute the air at the expense of Singaporeans' health and wellbeing."