BEIJING, Feb. 15 -- China's environmental watchdog said on Saturday that 33 of the 161 cities monitored nationwide were hit by heavy air pollution on the Lantern Festival, due to firework revelry and unfavorable weather conditions.

Beijing, together with its surrounding cities such as Shijiazhuang, Baoding, Xingtai and Hengshui, was rated by the Ministry of Environmental Protection as "severely polluted" on Friday, according to the ministry.

The Lantern Festival, which falls on Friday and marks the end of China's half-month lunar new year celebrations, traditionally features outdoor celebrations by lighting hanging lanterns and fireworks.

Chinese people traditionally believe the noise of setting off fireworks can fend off evil spirits and bad luck. However, fireworks' contribution to air pollution has drawn attention from the public and authorities over the past years.

The major pollutants were PM 2.5 and PM 10, and firework revelry was blamed for the serious air pollution, the ministry said.

Shijiazhuang, capital of north China's Hebei Province, was the most polluted city, with an average PM 2.5 reading of 363 micrograms per cubic meter.

An unidentified official with the ministry said the northern Tianjin-Hebei region will continue to suffer mild to moderate air pollution on Sunday and Monday due to unfavorable atmospheric conditions.

Beijing will see heavy to severe air pollution over the following two days, the official added.