China's environmental watchdog on Saturday publicized the names of 72 companies that have violated environmental protection regulations and says it plans to punish the offenders.

The companies, including PetroChina's Hohhot Petrochemical Corporation and the Datong Coal Mine Group, have committed 91 illegal acts, such as irregular use of pollution treatment facilities, excessive discharge of pollutants and improper handling of hazardous waste, according to a statement from the Ministry of Environmental Protection.

Of the identified companies, one steel company in northeast China's Heilongjiang Province and a sewage treatment plant have been fined and punished, and three starch factories in Heilongjiang have been shut down, the ministry said.

Their illegal practices were uncovered during a campaign initiated by the ministry in May to overhaul companies in 20 provincial regions across China.

Another 114 companies were found to have existing problems in their environment management practices.

The ministry urged local environment authorities to hand "deserved" punishments to these companies and to ask them to correct their practices.

Those who do not correct the problems in due time will be reported to supervision authorities for further sanctions, the ministry said.