A general view of buildings in Puxi district from the Jin Mao Tower amid heavy smog in Shanghai. REUTERS/Aly Song

SHANGHAI (Reuters) - China detained 720 people and Beijing imposed $21.8 million of fines for violating environmental protection laws in 2016, according to domestic media on Thursday.

China is in the third year of a “war on pollution” aimed at containing the damage done to its air, soil and water after decades of rapid economic growth. Just last week, Beijing faced severe pollution alerts, which forced people to stay indoors.

In 2016, 720 people were detained in China for damaging the environment, the official Xinhua news agency reported, citing information disclosed at a national environmental work conference.

The agency added that Beijing rejected 11 projects worth 97 billion yuan ($14 billion) due to environmental concerns last year.

Meanwhile, Beijing filed 13,127 environmental protection cases last year, with fines totaling $21.8 million, the Shanghai Daily said in a separate report citing local environmental authorities.

For 10,184 cases, fines of 8.7 million yuan were imposed for pollution from mobile emission sources, said the paper.

Of these, more than 10,000 vehicles were punished for excessive exhaust emissions, the paper added.

Hundreds of flights were canceled and highways closed across northern China over the new year holiday as average concentrations of small breathable particles known as PM2.5 soared above 500 micrograms per cubic meter in Beijing and surrounding regions.

(This version of the story has been refiled to delete extraneous word “dollars” in first paragraph)