The country is facing mounting pressure to control its pollution, despite progress made in cleaning up the environment, a senior official said on Thursday.

Vessels clean up floating waste and duckweed on the Yangtze River in Fengjie county, Chongqing municipality, in this file photo.?[China Daily]

China's sulfur dioxide emission, a major air pollutant, saw a 1.2 percent year-on-year increase in the first quarter - the first time it rose since 2007, said Zhang Lijun, vice-minister of environmental protection.

"This sounds the alarm for our emissions reduction work and shows that the situation is not very optimistic," Zhang told a press conference.

The increase was the result of rapid growth in the industrial output of a number of resource-intensive sectors, the major drought in the country's southwest region and slackness in the environmental awareness of some local governments and enterprises, Zhang said.

By the end of last year, the emission levels of COD and sulfur dioxide, major indicators for water and air pollution, fell 9.66 percent and 13.14 percent, respectively, from 2005 levels, according to the Ministry of Environmental Protection.

China has set binding targets to cut emissions of the both pollutants by 10 percent between 2006 and this year.

Zhang said the country will continue to enforce the "accountability system" that will hold local officials responsible if a region fails to reach its pollution reduction goals.

"The accountability system is a crucial mechanism that facilitated the progress made in slashing the pollution emissions in previous years," Zhang said.

In May, the ministry listed the provinces that did a poor job in reducing pollution emissions in 2009 and announced measures to penalize them, Zhang said.

China still faces severe environmental challenges, Zhang said. For instance, the country's surface water is still heavily polluted and offshore seawater is slightly polluted. Some cities still suffer from serious acid rain pollution.

Last year, the ministry rejected 49 projects over environmental concerns, involving 190 billion yuan. Those involved in 1,824 projects carried out without getting environmental reviews were also punished.

Similarly, the government shut 231 heavy-metal polluters and halted the operations of 641 firms. About 10,000 cases involving violations of environmental laws were filed and 119 people were held responsible.