The algae bloom has expanded by about 50 percent since it was first reported by state media earlier in June to 320 square kilometres, or about four times the size of Hong Kong island, Xinhua news agency said.

A large expanse of green algae is floating towards China's east coast, potentially threatening marine life and the region's tourism industry, an official and state media said Wednesday.

The algae covers 130 square kilometres (50 square miles) off the eastern provinces of Shandong and Jiangsu, the Global Times said, citing a spokesman for the North China Sea Branch of the State Oceanic Administration.

An official in the forecasting department of the agency told AFP the size of the algae was "likely to turn out to be larger than that" reported by the newspaper, but "should be similar to regular years".

Algae blooms are typically caused by pollution in China and suck up huge amounts of oxygen needed by marine wildlife to survive, while leaving a foul stench when they wash up on beaches.

In August 2008, a large offshore algae bloom threatened the sailing competition of the Olympic Games when it engulfed waters surrounding the event's venue in the coastal city of Qingdao in Shandong province.

Up to 10,000 soldiers and volunteers were enlisted to clean up more than a million tonnes of the foul-smelling algae as they raced to clear the waters in time for the Olympics.

An algae bloom also hit Qingdao in the springs of 2009 and 2010. More than a thousand dry-weight tonnes of algae was cleaned up last year alone, the city government has said.

Explore further Giant green algae slick heads towards China

(c) 2011 AFP