Beijing's local government thanked the city's residents yesterday, as a three-day pollution red alert expired and blue skies returned.

Many had been forced to leave their cars at home and find carers for their children because of measures triggered by the unprecedented red alert, such as restricting vehicle usage and shutting schools.

"The dedicated spirit and full support of the residents have deeply moved us," said Beijing's government in a notice posted online. "The municipal government and leaders express our sincerest gratitude and highest respect."

China's capital had been choking on hazardous air since Tuesday. The authorities said the red-alert measures cut pollutant emissions by 30 per cent on the first day alone, but pollution levels remained hazardous.

By the time the measures were lifted at noon yesterday, the air quality index that measures levels of harmful PM2.5 particles had dropped below 100 in most parts of city, according to data compiled by the US Embassy in Beijing.

"Green hills are beautiful, blue skies are joyous. Let us unite to declare war on environmental pollution," the government notice said.

The careful tone it struck underscores the sensitivity surrounding air pollution, which has become a major source of unhappiness among urban Chinese. The spell of bad air this month has had critics charging that the authorities are not doing enough to stop the pollution from industries in the provinces surrounding Beijing.

But Beijing vice-mayor Li Shixiang yesterday denied that there was resistance from surrounding areas. At a press conference, he said: "In terms of air pollution control, everyone has already formed a broad consensus."

Beijing will not be able to breathe easy for too long, as bad air is forecast to return tomorrow and linger until, at least, Monday.

"Two days," one Chinese netizen was quoted posting on social media Weibo. "Only two days of blue sky."