Chinese authorities have given courts the powers to hand down the death penalty in serious pollution cases, state media said, as the government tries to assuage growing public anger at environmental desecration.

An increasingly affluent urban population has begun to object to China's policy of growth at all costs, which has fuelled the economy for three decades, with the environment emerging as a focus of concern and protests.

A new judicial interpretation which took effect on Wednesday would impose "harsher punishments" and tighten "lax and superficial" enforcement of the country's environmental protection laws, the official Xinhua news agency reported.

"In the most serious cases the death penalty could be handed down," it said.

"With more precise criteria for convictions and sentencing, the judicial explanation provides a powerful legal weapon for law enforcement, which is expected to facilitate the work of judges and tighten punishments for polluters," Xinhua said, citing a government statement.

"All force should be mobilized to uncover law-breaking clues of environmental pollution in a timely way," it added.

Previous promises to tackle China's pollution crisis have had mixed results, and enforcement has been a problem at the local level, where governments often heavily rely on tax receipts from polluting industries under their jurisdiction.

Protests over pollution have unnerved the stability-obsessed ruling Communist Party.

Thousands of people took to the streets in the southwestern city of Kunming last month to protest against the planned production of a chemical at a refinery.

Severe air pollution in Beijing and large parts of northern China this winter have added to the sense of unease among the population.

Human rights groups say China executes thousands of people a year, more than all other countries combined. The death penalty is often imposed for corruption and other economic crimes. - Reuters, June 20, 2013.