China closed down a total of 3,176 polluting enterprises amid a campaign in which 720,000 companies have been checked for their pollution discharges last year, according to the country's top environment watchdog.

In the campaign, the State Environmental Protection Administration (SEPA) and other departments investigated 28,000 cases violating related environmental laws and regulations and settled 13,000 of the total.

Threats to the sources of drinking water, industrial parks densely distributed with polluting enterprises and construction projects likely to damage the environment were the major targets in the campaign, according to the administration.

"Pollution by industrial parks has been curbed effectively," said an official with the administration.

A total of 1,981 industrial parks across the country, involving 29,890 enterprises, were subject to investigation, and 4,162 polluting companies got severe punishment, the official said.

Other six ministerial departments, including the Ministry of Supervision, participated in the campaign.