Dead zones are areas in oceans and lakes choked of oxygen by algae blooms that feed off high concentrations of pollutants such as raw sewage and fertilizer, the report said.

The algae blooms sap the water of its oxygen, which in turn endangers marine life, it added.

According to a separate report by China's State Environmental Protection Administration, the nation's coastal regions suffered from 82 "red tides", a form of algae bloom, in 2005, the paper said.

Large-scale red tides have become an annual occurrence in waters off eastern China's Zhejiang province, where the Yangtze River flows into the sea, and farther north in the Bohai Sea near the Yellow River estuary, the paper added.

Last year, land-based activities in China led to the dumping of 500,000 tons of ammonia-nitrogen and 30,000 tons of phosphate into the sea, it said. The two chemicals are key ingredients in fertilizer.

In June this year, a red tide that spread out in a 1,000-square-kilometre (620-square-mile) area in the Yangtze River estuary killed more than 12 million fish.

The spread of the tide led to safety warnings in Shanghai about eating seafood from the area, the paper said.

More than 20 years of robust economic growth in China have come at the expense of the environment, with local governments and industries shunning ecological protection in the pursuit of short-term profits.

The central government often cites this as a major problem and says it is taking action, but the nation's environmental woes continue to worsen.

Meanwhile, the leading People's Daily reported Friday that it would take at least 200 years to clean up the Bohai Sea, even if no more sewage was poured into it.

The body, located some 150 kilometers (90 miles) east of the capital Beijing, was named the "worst polluted" sea area in China after an investigation by the State Oceanic Administration, the paper said.

Industrial sewage, pesticides, fertilizers and the dumping of garbage had gravely polluted it, the paper added.

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