The Philippines decried China’s plan to develop and fortify a vast area of the potentially resource-rich South China Sea, a move from Beijing that could stoke tensions in the disputed waters.

China said this week it will invest at least $1.6 billion for the construction of a harbor, an airport and other facilities in the areas. The investment has been criticized by the Philippines as lacking “merit under international law”.

“This is giving a lot of concerns among nation states not only in the region but as far as the international community is concerned,” Foreign Affairs spokesman Raul Hernandez told reporters on Wednesday.

China’s recent plan was “a way of reinforcing their nine-dash line claim which is considered excessive and a violation of international law,” Hernandez said, adding that “This action will not gain validity for China”.

Beijing has established a new city called Sansha to politically administer territories in the South China Sea where the Philippines, Vietnam, Malaysia, Brunei and Taiwan have overlapping claims.

The territorial dispute in the South China Sea has become the biggest military flashpoint in the region amid China’s growing assertiveness in claiming territories.