Vietnam's move to build an airport on Nansha islands will further complicate the situation in the South China Sea, said Chinese Foreign Ministry spokesman Liu Jianchao Tuesday.

Liu said at a regular news conference that China holds a clear-cut stance over the issue of the Nansha islands, and China has full historical and legal evidence to prove that it possesses indisputable sovereignty over the Nansha islands and surrounding waters.

Vietnam's move has not only infringed upon China's territorial sovereignty and is illegal and invalid, Liu said, and this move also violated the commitments enshrined in the Declaration on the Conduct of Parties in the South China Sea between China and the Association of Southeastern Asian Nations (ASEAN).

It is reported that Vietnam has begun building an airport at an island of Nansha islands, and the project is expected to finish by the end of this year.