At least three flight schedules were delayed in Riau of Sumatra due to poor feasibility incurred by haze from land clearing and the satellite observation shows a steep rise in the number of hot spots on Sumatra and Borneo islands, officials said here on Wednesday. Several of the hot spots are located in forest conservation areas on the Sumatra island, including in the provinces of Riau, North Sumatra, Aceh, Jambi, and South Sumatra, Sutopo Purwo Nugroho, spokesman for the national disaster agency, said. "The feasibility in Riau was less than 500 meters so that the flight witnessed disruption. Yesterday (Tuesday) three flight schedules of Garuda Indonesia, Lion Air and Air Asia were delayed, " he told Xinhua via phone. According to a satellite observation, the hot spots scaled up and more than doubled to 470 on Tuesday on Sumatra and Borneo islands from 187 a day earlier, said Sutopo. Indonesia has been battered by fires resulting from land clearing for new plantations since the 1990s, with haze caused enveloping neighboring ASEAN countries that hampered business spheres and incurred multi-billion U.S. dollars of financial loss. Indonesian authorities would take comprehensive measures, including using water bombs, modifying weather and enforcing law, to extinguish ongoing fires on Sumatra and Borneo islands in an effort to prevent a repeat of haze enveloping neighboring countries like years ago from happening, Sutopo said. The condition of the dry season this year, which is forecast to be drier than in previous years, and weak El Nino, are threatening to exacerbate the spread of fire, he said.