China’s military has begun military exercises near an area in the South China Sea that both China and the Philippines claim sovereignty over. The Southern Theatre Command announced on Wednesday that it has conducted air and sea patrols “near Huangyan Island”—China’s name for Scarborough Shoal—to test “attack capabilities.” These exercises appear to be a response to concurrent military maneuvers carried out by the United States, Australia, Canada, and the Philippines. The Chinese military stated that the operations aimed to assess troops’ reconnaissance and early warning abilities.

“All military activities that disrupt the South China Sea create hotspots and undermine regional peace and stability and should be controlled to the greatest extent possible,” they noted.

In a joint statement, military leaders from the United States, Australia, Canada, and the Philippines declared that they “stand united to address common maritime challenges and emphasize our shared commitment to upholding international law and a rules-based order.” They mentioned that the two days of exercises were held to ensure unimpeded passage in the Pacific region.

Beijing and Manila have faced heightened tensions in recent months as China continues to assert claims over almost the entire South China Sea, despite an international court ruling that determined that China’s claims have no legal basis. Scarborough Shoal is located 240 kilometers (about 150 miles) west of the Philippines’ main island of Luzon and nearly 900 kilometers (approximately 560 miles) from the nearest major Chinese landmass, Hainan.

In 2012, China dispatched coast guard vessels to take control of the shoal, which had previously been a safe haven for Filipino fishermen. Confrontations have also centered around a warship that Manila has intentionally run aground for years at the disputed Second Thomas Shoal. In June, Chinese coast guard personnel armed with knives and axes boarded Philippine warships near the strategic reef, resulting in a sailor losing a thumb and Filipino equipment being seized or destroyed.

Beijing has blamed Manila for the escalation, asserting that their actions are legal and proportional. Last month, the United States announced it would provide an additional $500 million in military support to the Philippines to counter China’s increasingly aggressive behavior in the region. Beijing responded, stating that “drawing in countries from outside the region to provoke confrontation… will only undermine regional stability and exacerbate tensions.” They warned that this investment “will only lead to greater insecurity” for Manila.

In addition to China and the Philippines, Vietnam, Malaysia, Brunei, and Taiwan are engaged in separate yet escalating territorial disputes in these waters, which are viewed as a potential flashpoint and a delicate fault line in the U.S.-China regional rivalry. For decades, the U.S. military has conducted naval patrols and flights, which they label as freedom of navigation, but which China opposes and views as a threat to regional stability.