Doctors in Beijing said Thursday that hospital admissions for respiratory complaints rose in recent days during the latest bout of pollution, as air quality in the city began to improve.

The US embassy's air quality index stood at 233 on Thursday morning, or "very unhealthy", after it peaked at more than 500 on Tuesday. The Beijing municipality's figure was 184 at 10:00 am on Thursday, or "lightly polluted".

Beijing and vast swathes of China have experienced several bouts of heavy pollution over the last month, lowering visibility and leading to transport disruption.

The number of patients admitted to several hospitals in Beijing complaining of respiratory problems rose 20 percent "in recent days," the Beijing Morning Post reported.

Half of those admitted to a children's hospital in Beijing were suffering from respiratory infections, the newspaper said.

The pollution in the capital has been blamed on emissions from coal-burning in power stations, and exhaust fumes from vehicles on Beijing's choked streets.

Beijing has ordered the emergency closure of factories and removed government vehicles from the streets in an effort to reduce the haze, but experts say more radical controls are needed to effectively combat the problem.

China's meteorological agency said the smog in Beijing was likely to disperse on Thursday evening when the city will be hit by strong winds.