KUALA LUMPUR -- The Malaysian government summoned China's ambassador to formally protest alleged encroachment into its South China Sea waters by Chinese vessels, the Ministry of Foreign Affairs announced on Tuesday.

Despite overt displays of warm ties earlier this year, Putrajaya registered its strong objection in a meeting with Ambassador Ouyang Yujing on Monday. The ministry said it had detected the presence of Chinese vessels, including a survey ship, in Malaysia's exclusive economic zone off the coasts of its Bornean states.

"Malaysia's consistent position and actions are based on international law, in defense of our sovereignty and sovereign rights in our waters," the ministry said in a statement. "In determining Malaysia's position and course of action with regard to the South China Sea issue, which is complex and involves inter-state relations, Malaysia's national interests will remain of paramount importance."

The flare-up in the dispute takes the new Malaysian government of Prime Minister Ismail Sabri Yaakob into difficult territory. While standing by its maritime rights, Kuala Lumpur has sought positive relations with China of late, including in the fight against COVID-19. When previous Foreign Minister Hishammuddin Hussein met with Chinese counterpart Wang Yi earlier this year, he described the relationship as one with a "big brother."

Giving the Chinese Foreign Ministry's account of the Hishammuddin-Wang meeting in April, spokesperson Hua Chunying said the two had agreed to work together to "safeguard peace and stability in the South China Sea."

China consistently denies acting inappropriately in the sea -- a critical waterway for global shipping and fishing, where Beijing has overlapping claims with several Southeast Asian countries including the Philippines and Vietnam. In a statement to the United Nations in September 2020, Beijing said that "China's territorial sovereignty and maritime rights and interests in the South China Sea are established in the long course of history" and were "consistent with international law."

But Malaysia's ministry on Tuesday argued the Chinese vessels' presence breached the 1982 United Nations Convention on the Law of the Sea (UNCLOS) and the country's own Exclusive Economic Zone Act of 1984.

Although China claims most of the sea under its "nine-dash line," global regulators insist the waters belong to multiple countries and that a code of conduct should be established to avoid conflict. An international tribunal in The Hague found in 2016 that the nine-dash line lacks a legal foundation -- a decision China has refused to accept.

In 2016, China was alleged to have conducted a military exercise at the man-made Fiery Cross Island in the disputed sea, close to Malaysia's maritime border. Flight tests and landings conducted by China on the island created unease among the other claimants and increased tensions.

Malaysia's Foreign Ministry reiterated that all matters relating to the South China Sea must be resolved peacefully and constructively, in accordance with universally recognized principles of international law.