By Agence France-Presse Health officials in Serbia warned on Sunday about the risks of "very high" levels of air pollution in Belgrade and several other cities, a problem also being experienced in neighbouring Bosnia and North Macedonia. A man rides a bicycle on one of Belgrade's bridges (AFP Photo/Oliver BUNIC) A thick cloud of pollution has been visible over the city for several days now, and according to the AirVisual app, Belgrade has several times in the last week been among the most polluted cities in the world. The Serbian Environmental Protection Agency said air pollution had been high for several days in the capital because of unusually warm weather. Levels of particulate matter (PM10) were higher than 200 microgrammes per cubic metre in Belgrade and its suburbs, where more than 1.6 million people live, the agency said. Those levels of air pollution are bad enough to affect not just people with pre-existing conditions but the whole population, it said. "We have noted for about 10 days a rise in respiratory infections," Snezana Rsovac, a doctor in a Belgrade paediatric clinic, told RST television. High atmospheric pressure and an absence of wind had kept the pollution in place, Andrej Sistaric of the Belgrade public health institute told RTS. Conditions were not likely to significantly improve before Tuesday and a change in the weather, said the experts. Contributing factors appeared to be the burning of farmland to clear the land for more crops and a fire that broke out at a council rubbish dump in Belgrade. It was a similar story in other Serbian cities, including Novi Sad, Panceov and Subotica in the northern half of the country, and Uzice in the southwest. The Bosnian capital Sarajevo and North Macedonia's capital Skopje were experiencing a similar problem. Both cities have a chronic air pollution problem because of the widespread use of wood as heating fuel.