A worsening haze across northern Indonesia, neighboring Singapore and parts of Malaysia on Tuesday forced some schools to close and airlines to cancel flights, while Indonesia ordered a crackdown against lighting fires to clear forested land.

Southeast Asia has suffered for years from annual bouts of smog caused by slash-and-burn practices in Indonesia's Sumatra and Kalimantan islands, but governments in the region have failed to address the problem.

The fires have been exacerbated this year by the effects of the El Nino weather phenomenon, as a prolonged dry season in Indonesia has parched the top soil, fueling the flames.