Singapore rolled out subsidies for haze-related medical treatment Monday and schools were closed in parts of neighbouring Malaysia, as both countries grapple with persistently unhealthy air quality due to fires in nearby Indonesia.

Singapore again ranked the world's most polluted city on Monday, according to Swiss-based air quality monitor IQAir, as the fires on Borneo and Sumatra islands, intensified by a turbo-charged El Nino weather phenomenon, keep emitting toxic haze.