Thick smoke from wildfires caused by illegal land clearing in Indonesia is making thousands of people sick. South Sumatra, one of the main centres of the fires, has reported 22,585 cases of acute respiratory tract infections in the last 24 hours.

The haze is delaying flights and pushing air quality to unhealthy levels in neighbouring Singapore and Malaysia. Singapore's Pollutants Standard Index rose to 248, which categorises the air as "very unhealthy", or one level below the index's highest air pollution category of "hazardous". Citizens have been advised against strenuous outdoor exercise.

Indonesia has said it will send more than 10,000 troops to fight fires in southern Sumatra. Indonesian troops will be sent to the provinces of South Sumatra and Jambi, two of the main hotspots, Indonesia's National Disaster Mitigation Agency (BNPB) said. If necessary, the agency would also send in additional helicopters to help water-bomb fires.

The south east Asian country has vowed before to end the seasonal fires but has failed each time to stop the so-called "haze", caused by slash-and-burn clearances on the islands of Sumatra and Borneo, where large areas of forest are held by pulp and paper and palm oil companies