Hong Kong urged residents to stay indoors Thursday as the city choked under the worst cloud of man-made air pollution the city has ever recorded, officials said. Air pollutant readings broke records going back to 1999, except for levels reached when a natural dust storm hit the southern Chinese city two years ago, environmental protection department spokesman Y.F. Chau said. \"This is the worst air pollution reading we\'ve seen since Hong Kong started recording air pollution in 1999, except for the dust storm,\" he said. Hong Kong\'s famous skyline was shrouded in a dense blanket of toxic haze and the sky looked grey, although the weather was fine and sunny. \"People with heart or respiratory illnesses, the elderly and children should reduce physical exertion and outdoor activities,\" a government spokeswoman said. Officials said the pollution had been exacerbated by the influence of Typhoon Saola, which killed four people as it lashed Taiwan some 700 kilometres (450 miles) to the east. The storm\'s outer high-pressure air mass blanketed Hong Kong, bringing strong sunshine and high temperatures that resulted in elevated ozone levels. Anti-pollution activists said Hong Kong could not keep blaming the weather or factories in neighbouring mainland China for its recurring pollution problems. \"If Hong Kong did not produce air pollutants, the weather conditions would not be able to exacerbate or cause further consequences,\" Clean Air Network campaign manager Erica Chan told AFP. Emissions from local vehicles using old and dirty engines are among the main contributors to Hong Kong\'s air pollution, she said. The government announced revisions to its air quality objectives for the first time in 25 years in January, after University of Hong Kong research showed pollution-related illnesses killed more than 3,000 residents a year.