"The Spoon-billed Sandpiper and Nordmann's Greenshank face extinction as their remaining populations rely on the tidal-flats of the Yellow Sea and on Saemangeum in particular, UK-based RSBP said in a report at the weekend.

The two groups said the project has led to a loss shellfish, fish and plants for the shore birds who used to stop there during their journeys between Russia and Asia.

Some species, such as the Great Knot, may not be able to put on weight and their breeding may suffer.

"These birds could be too poorly fed this year to survive their final flight north," it said.

Lee Jeong-yeon, an official with the South Korean government affiliated National Institute of Environmental Research, agreed the reclamation project had hurt migratory birds.

But he said the wetlands had not been completely destroyed and that the government was trying to develop nearby wetlands to make sure the birds can find food during their trips.

South Korea, now one of the world's largest economies, launched its reclamation projects decades ago to increase its farm land when it was a poor country trying to rise from the ashes of the 1950-1953 Korean War to feed itself.

Bird Korea, which has conducted counts in the Saemangeum area, said the number of shore birds which have visited for the current March to May migration season has been about 50,000 so far, down from 150,000 in the same period a year ago.

Nial Moores, a U.K.-born conservationist who is the director environmental group, did not accept the government's argument that the shore birds would find new places to stop.