Caishikou Street in Beijing shrouded by smog on Sept 29 and in clean air on Sept 25. Beijing has been hit hard by severe pollution since the start of the year. [Photo/Xinhua]

BEIJING -- Beijing on Sunday was shrouded in choking smog due to adverse weather conditions in the capital city as well as in neighboring regions, meteorologic authorities said.

As of 8 am, 24 out of 35 monitoring spots in the capital indicated heavy air pollution with the highest level of six, according to the Beijing Municipal Environmental Monitoring Center.

The density of airborne particles measuring less than 2.5 microns in diameter, or PM 2.5, exceeded 200 micrograms per cubic meter, the center said.

It suggested the public avoid driving.

Car emissions are considered one of the major air polluting sources in Beijing, contributing more than one fifth of the PM 2.5 particles.

The number of automobiles in the city was more than 5.37 million at the end of August.