Vietnam is protesting China's decision to post bids on offshore oil blocks in the disputed South China Sea.

The China National Offshore Oil Corporation on Saturday announced that nine oil and gas lots were open for exploration.

Vietnam's foreign ministry said in a statement the blocks lie entirely within Vietnam's exclusive economic zone and continental shelf. It said Beijing's announcement violates Vietnam's sovereign rights, jurisdiction and national interests.

China said it hopes Vietnam avoids actions that will complicate the matter further.

Vietnam and China are among several nations with territorial claims in the South China Sea. The area is home to vast fishing grounds and potential oil and gas deposits.