Chinese President Xi Jinping boasted of a closer, more robust bilateral relationship with Russia Wednesday, remarking that he and counterpart Vladimir Putin had agreed to “strengthen mutual support on major issues” as the two nations engage in military exercises in the South China Sea.

“No matter how the international situation or the external environment changes, both countries need to work hard to realize their goals of development and revitalization and to safeguard world peace and stability as well as international equity and justice,” Chinese state news outlet Xinhua quotes Xi as stating. Referring to a conversation he had with Putin during this month’s G20 Summit in Hangzhou, China, Xi said, “Both of us agreed that China and Russia need to strengthen mutual support on major issues and consolidate political mutual trust.”

Xi has been pushing to develop both military and economic relations with Russia. In June, the two nations announced that they had sealed trade deals with $50 billion between their two countries. “The stance of Russia and China is quite close, and even sometimes, we are in the same position, in terms of international affairs. We will continue dialogue on international issues,” Putin said at the time.

Xi’s reassurances that the relationship between Russia and China is strong and growing come as the two nation’s militaries partake in joint maritime exercises off the Chinese coast in the South China Sea. Russian propaganda outlet RT reports that Thursday was the first day of the “active phase” of the exercises, in which the two nations executed a mock invasion of an enemy stronghold.

The joint exercises are an annual occurrence, though both nations are citing these as the largest in history – the result of a blooming relationship between Xi and Putin, who have met personally 17 times since 2013.

“The drill will culminate in a joint amphibious and aerial assault on a fortified island,” RT confirmed.

The simulated invasion of a foreign island is causing some international alarm, as China has spent the past three years trying to usurp ownership of much of the territory in the South China Sea. dBeijing claims islands and shoals that belong to Malaysia, Brunei, Taiwan, Vietnam, and the Philippines, and has created artificial islands in the Spratly and Paracel Island chains, belonging to the Philippines and Vietnam. Those islands have been fortified with surveillance equipment, surface-to-air missiles, and fighter jets.

The Permanent Court of Arbitration at The Hague ruled against China in July, finding that none of the nation’s claims in the contested regions were legitimate and ruling in favor of the Philippines. At the G20 Summit, Putin made clear that Russia agreed with China’s policy of disregarding The Hague entirely.

“We stand in solidarity and support of China’s position on this issue – not to recognize the decision of this court … arbitration proceedings should be initiated by the disputing parties, while the arbitration court should hear the arguments and positions of the disputing parties,” he argued. Putin added that Chinese officials had not prodded him to give a public opinion on the matter.

What China had done in April of this year was cite vague proclamations by Russian Foreign Minister Sergei Lavrov that China and the disputing parties should use “negotiation and consultation” to argue that The Hague ruling should be ignored, even before it was handed down.

Russian officials have downplayed any potential alarm concerning the joint exercises. “We believe that all actions which take place there must be pondered, balanced and not add instability, but rather work on strengthening stability and mutual understanding to solve conflicts,” Xinhua cites a Russian Foreign Ministry spokeswoman as stating Thursday.