The environmental group Greenpeace has started dropping boulders into EU-protected cod fishing grounds off Sweden to prevent seabed trawling, local media reported Tuesday.

The group plans to sink 180 boulders weighing between two and three tons into the North Sea off the Swedish coast in response to allegations that trawl nets used by fishermen cause serious damage to marine wildlife, according to the Swedish electronic newspaper The Local.

"The operation in Kattegat sea area, which is about 20 kilometers off the Swedish southwest coast, began at 11:30 a.m. on Monday. We have informed regional officials about the operation between Sweden and Denmark, and it would have no negative impact on the environment," Greenpeace spokesman Staffan Danielsson was quoted by The Local as saying.

Greenpeace has urged Sweden to reform the EU's fisheries policy in the beginning of its six-month EU presidency last month.

(Xinhua News Agency August 12, 2009)