Beijing, Feb 4 (IANS/EFE): The number of people admitted to hospital with respiratory problems has increased 20 percent in Beijing following the intense smog that blanketed the city in January, a media report said.

Beijing Morning Post Saturday gave the example of a children's hospital in the Chinese capital where more than half the patients were suffering from respiratory infections.

Though skies over the capital have been blue since the month began, the pollution in January exceeded the worst alert levels and led to an official request that citizens not go outside into the streets.

Authorities also ordered 30 percent of official vehicles off the roads and suspended operations at 103 highly contaminant factories.

Last month Beijing recorded historic highs of pollution, specifically Jan 12 when the concentration of PM2 particulates reached 993 micrograms per cubic meter of air (the World Health Organization considers concentrations below 25 micrograms per cubic meter acceptable).

All of which sparked the anger of Beijing residents, who have communicated their indignation on social networks, while even official media have called on city officials to take "concrete action".

The China Daily newspaper urged the Chinese government Friday to reveal the full details and causes of the pollution "if it really wants to tackle the problem seriously".

The city's constant air pollution is attributed to emissions from nearby coal-burning power plants and fumes from vehicles in the streets of the capital.