Chinese President Xi Jinping has called for strengthened efforts to curb air pollution during a tour of Beijing through heavy smog.

Accompanied by officials from both central authorities and the Chinese capital, Xi visited a trendy alley in downtown Beijing on Tuesday and walked along the banks of a nearby river. He also visited Beijing City Planning Exhibition Hall and a water plant.

Beijing and other areas in north China have been shrouded in heavy smog in recent days. On Tuesday, the city maintained an orange pollution alert, as the density of PM2.5, or particles smaller than 2.5 microns in diameter, measured over 400 in the city proper.

The heavy air pollution eased on Wednesday evening as a cold front arrived.

When visiting the water plant, Xi said environmental protection in the megacity of Beijing is a job for systematic engineering, and much attention should be paid to it as air pollution is a major issue concerning people's livelihood.

"We should treat both symptoms and root causes of environmental pollution, and we should also focus both on emergency and regular measures," said the president, adding that the issue should be addressed through coordination between different areas and with action by the whole society.

At a symposium after the tour on Wednesday, Xi called for strengthened efforts to control smog. He said the priority is to limit PM2.5 by reducing dependence on coal, strictly controlling vehicles, adjusting industry structures, and other measures.

He also urged related departments to strictly implement an index system that evaluates authorities' and officials' performances, and to strengthen law enforcement on environmental issues.