Singaporeans are rolling back military training, keeping cough-stricken children indoors and considering wearing protective masks to work after a smoky haze triggered by forest fires in neighboring Indonesia caused air pollution to briefly hit its worst level in nearly 16 years.

Singapore's main measure to determine air quality has crept into the "unhealthy" classification as smoke from roaring blazes on Indonesia's Sumatra island drift across the sea and cast a gray pall over the city-state's skyscrapers.

The index reached a reading of 155 Monday night, the highest level since late 1997.

At midday Tuesday, the reading eased to 114, still within the "unhealthy" range of between 101 and 200.

Smoke haze from Indonesia is a nearly annual problem for Singapore and its northern neighbor Malaysia.