Hospital admissions for respiratory complaints rose 20 per cent in the latest smog to hit Beijing, reports said yesterday as state media demanded greater government openness on pollution. This week's pollution across vast swathes of the northern mainland region - the fourth serious case of toxic air in recent weeks - has sparked online anger and prompted unusually outspoken calls for action, even from official media. The number of patients admitted to several hospitals in the capital for breathing problems rose by a fifth in recent days, the Beijing Morning Post reported. Half of those admitted to a city children's hospital were suffering from respiratory infections, the newspaper said, citing doctors. State broadcaster CCTV quoted Zhong Nanshan , the president of the China Medical Association who revealed the cover-up of the Sars epidemic of 2003, as saying: "Air pollution is much more scary than Sars, and affects the heart and veins." Sars (severe acute respiratory syndrome) infected 1,755 people in Hong Kong and 299 died. Worldwide, there were 8,098 cases across 29 countries with 774 deaths. The China Daily urged the government to reveal details of the causes of the pollution, saying departments had yet to provide credible data. Without such information "the government's promise to tackle the problem may fail to materialise", it said. The pollution in the capital has been blamed on emissions from coal-burning in power stations and exhaust fumes from vehicles on choked streets. The elderly, young and those with health problems in the city of 20 million were urged to stay indoors earlier in the week - or wear protective masks if they had to venture out - while dozens of flights were cancelled after visibility fell drastically. Beijing ordered the emergency closure of factories and removed government vehicles from the streets to try to reduce the haze, but experts say more radical controls are needed to combat the problem effectively. Real estate tycoon and internet blogger Pan Shiyi - who has 14 million followers on Sina Weibo, a mainland version of Twitter - started a campaign for clean air legislation. It had attracted more than 46,000 signatures as of yesterday afternoon. Social media users reacted angrily to comments from an official at the Ministry of Environmental Protection, who said developed countries took up to 50 years to solve their pollution problems. "It will take years and years and cost taxpayers all their money," one user wrote. Traffic policemen urged officials to change the dress code and let them wear masks on duty, the China Daily reported. The US embassy's air quality index in Beijing stood at 207 yesterday afternoon, or "very unhealthy", after it peaked at more than 500 on Tuesday. Forecasters predicted that the smog would begin to disperse overnight as strong winds arrived.