China's environmental watchdog on Monday said it plans to punish 805 companies for violating environmental protection regulations.

These companies were identified during a massive monthly inspection in November, when the Ministry of Environmental Protection checked 29,285 industrial and catering companies in 37 cities across China, according to the ministry.

The names of 33 companies, including Ansteel Group's chemical branch in northeast China's Liaoning Province, were publicized by the ministry for serious air or environmental pollution.

Another 890 small workshops were shut down in the inspection, the ministry said.

Journalists had been invited to participate in the inspection, it said.

Four major illegal practices were found during the inspection, including irregular use of pollution treatment facilities, excessive discharge of pollutants, failure to upgrade technology and industrial capacities, and improper handling of hazardous waste and dust, according to the ministry.

The ministry said it will join local authorities in rectifying the illegal acts and punish "relevant staff."