BEIJING - China's Foreign Ministry on Monday urged Vietnam to refrain from taking any actions that complicate and escalate issues between the two countries, as a Vietnamese maritime law is due to become effective on Tuesday.

In a press release, ministry spokeswoman Hua Chunying stressed that China has indisputable sovereignty over the Xisha Islands, Nansha Islands and their adjacent waters in the South China Sea.

Any claim raised by any other country and any action taken by any other nation to territorial sovereignty over the islands and waters are illegal and invalid, she said.

Hua said that China is deeply concerned about the negative impact of the implementation of the law.

In June, the Vietnam National Assembly passed the "Vietnamese Law of the Sea," which describes China's Xisha Islands and Nansha Islands as being within Vietnam's sovereignty and jurisdiction.