Chinese Premier Li Keqiang on Thursday renewed pledges to tackle the country's chronic pollution, without announcing any significant new environmental measures.

The Chinese public are increasingly enraged by hazardous smog that regularly blankets cities, as well as water and soil that are laced with heavy metals and various other toxic pollutants.

"Environment pollution is a blight on people's quality of life and a trouble that weighs on their hearts," Li told the opening of the annual National People's Congress (NPC), the country's communist-controlled legislature.

"We must fight it with all our might," he said.

His comments came after an online documentary on China's notorious smog was released over the weekend criticising the government's action on the issue and immediately became a viral sensation, with 155 million views by the next day according to state media.

Authorities have since reportedly told Chinese media to tone down their coverage of the film.

Li's rhetoric resembled promises he made last year, when he declared a "war" on pollution, but the subject was not as prominent in his address, coming after other economic priorities.

China this year began enforcement of a new environmental law -- the first in 25 years -- imposing tougher penalties and pledging that violators will be "named and shamed".

Li pledged that the government would implement existing measures to tackle air pollution, and crack down on polluters and officials who sometimes connive with them.

"We must... crack down on those guilty of creating illegal emissions and ensure they pay a heavy price for such offences; and hold those who allow illegal emissions to account, punishing them accordingly," he said.

Recent studies have shown that roughly two-thirds of China's soil is estimated to be polluted, and that 60 percent of underground water is too contaminated to drink.

In a paper published in medical journal The Lancet, a retired health minister acknowledged that air pollution may lead to as many as half a million premature deaths each year.

China is also under international pressure to reduce its emissions of climate change-causing carbon dioxide, which are the largest in the world.

China has not pledged any absolute reductions in carbon emissions, but has said they will peak "around 2030".

It has also pledged that 20 percent of its energy would come from renewable sources by 2030, a colossal undertaking equivalent to powering the United States national grid purely through non-fossil fuels.

The share of non-fossil fuels in primary energy consumption reached 11.2 percent last year, up from 10.1 percent a year ago, according to a report submitted to the NPC Thursday by the National Development and Reform Commission, the country's top economic planning agency.

The amount of emissions per unit of GDP fell by 6.2 percent in 2014, it said.

Li said China expects to reduce that further by "more than 3.1 percent" this year, adding it aims to stop coal consumption growing "in key areas".