China released a legal opinion on Thursday, saying that the so-called maritime delimitation talks between Japan and the Philippines, which covers waters east of China’s Taiwan Island, constitute a severe violation of international law.

It comes amid a series of statements and actions from various Chinese ministries on the matter, since the talks were first announced in late May during Philippine President Ferdinand R. Marcos Jr.’s visit to Japan.

The report was issued by the China Institute for Marine Affairs, a think tank under the Ministry of Natural Resources. It says the proposed delimitation substantially overlaps with the exclusive economic zone and continental shelf to which China is entitled under international law, and argues that Japan and the Philippines’ attempt to bypass China constitutes a severe violation of the United Nations Convention on the Law of the Sea (UNCLOS), as well as other international laws and basic norms governing international relations.

The paper urges Japan and the Philippines to stop advancing the talks and to engage in consultations with China. It also warns them not to challenge the one-China principle under the pretext of “delimitation,” and says all other states should refrain from assisting Japan and the Philippines in what it describes as the commission of an internationally wrongful act.