A red tide has hit the coast of Xiamen, a major city in southeast China's Fujian Province, leaving masses of oysters and fish dead and the seas brown and smelly.

The city's first winter red tide in ten years covers more than ten square kilometers, but is expected disappear in three to four days, according to a report in Tuesday's Southeast Express newspaper.

The local marine authority said the red tide was not caused by poisonous algae, and would not affect local people because there were no marine farms in the area.

The Xiamen government did not give safety warnings about eating seafood, but said local residents were advised against swimming in the water.

The red tide was caused by increasing temperature and recent projects to clear seabed sludge, which may have stirred up fertilizer residues in the seabed and given rise to algal blooms, the newspaper quoted marine experts as saying.

The local government was installing facilities to help dissipate the algae and closely monitoring the waters, the newspaper said.

Red tides occur when pollutants such as raw sewage and fertilizers cause algae to bloom, sapping the water of oxygen and endangering marine life.

Large red tides have become an annual occurrence in waters off China's coastal regions, including 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.

China reported 93 red tides in 2006, an increase of 13 percent over the previous year.

(Xinhua News Agency January 17, 2007)