MANILA, Philippines (AP) — A Chinese coast guard ship and one of its militia vessels separately bumped a Philippine coast guard ship and a military-run supply boat Sunday off a contested shoal, Philippine officials said, in a serious flareup that could heighten fears of an armed conflict in the disputed South China Sea.

A top Philippine security official told The Associated Press there were no injuries among the Filipino crew members and an assessment of the damage to both vessels was underway.

The official added that the incidents near the Second Thomas Shoal could have been worse if they were not able to maneuver rapidly away from the Chinese ships. The official spoke on condition of anonymity due to a lack of authority to publicly discuss details of the incidents.

The United States, a longtime treaty ally of the Philippines, immediately condemned the actions by China’s ships. The Philippine government also condemned the latest confrontations in “the strongest degree” and called them a violation of Manila’s sovereignty.

The Chinese coast guard said the Philippine vessels “trespassed” into what it said were Chinese waters “without authorization” despite repeated radio warnings, prompting its ships to stop them. It blamed the Philippine vessels for causing the collisions.

“The Philippine side’s behavior seriously violates the international rules on avoiding collisions at sea and threatens the navigation safety of our vessels,” the Chinese coast guard said in a statement posted on its website.

The U.S. Ambassador to Manila, MaryKay Carlson, said in a post on X, formerly known as Twitter, that “the United States condemns the PRC’s latest disruption of a legal Philippine resupply mission to Ayungin shoal, putting the lives of Filipino service members at risk.”

She used the initials for China’s formal name, the People’s Republic of China, and the name the Philippines uses for the Second Thomas Shoal. She added that Washington was standing with its allies to help protect Philippine sovereignty and to support a free and open Indo-Pacific region.

A Philippine government task force dealing with the South China Sea disputes said the collisions occurred as two Philippine supply boats escorted by two Philippine coast guard ships were heading to deliver food and other supplies to the atoll in the face of a years-long Chinese blockade.

The task force said it “condemns in the strongest degree the latest dangerous, irresponsible, and illegal actions of the Chinese coast guard and the Chinese maritime militia done this morning in violation of Philippine sovereignty, sovereign rights and jurisdiction.”

The actions by the Chinese ships were “in utter blatant disregard of the United Nations Charter, the United Nations Convention on the Law of the Sea” and international regulations that aim to prevent sea collisions, said the Philippine task force, which includes the country’s defense and foreign affairs departments, the military, national security council and the coast guard.

Near-collisions have happened frequently as Philippine vessels regularly deliver supplies to Filipino marines and sailors stationed on the disputed shoal. But this was the first time Philippine officials have reported their country’s vessels being hit by China’s ships.

In the first incident that happened Sunday morning, “dangerous blocking maneuvers of China coast guard vessel 5203 caused it to collide with the Armed Forces of the Philippines-contracted indigenous resupply boat Unaiza May 2,” the task force statement said. It said the “provocative, irresponsible, and illegal action” of the Chinese coast guard ship “imperiled the safety of the crew.”

The Chinese coast guard gave a different version and said the Philippine supply boat deliberately crossed the bow of its ship, which was on a routine law enforcement patrol, “resulting in a slight collision.”

Separately, Philippine coast guard ship BRP Cabra’s left side “was bumped by Chinese maritime militia vessel 00003 while it was lying to” northeast of the Second Thomas Shoal, the statement said.

The Chinese coast guard said the Philippine ship “deliberately provoked trouble” by reversing its direction, causing its stern to collide with the Chinese vessel and “heating up the situation at the scene.” In the past, Chinese officials have played down claims that the Chinese vessels were military militia ships meant to look like fishing boats.

Despite the Chinese coast guard blockade, one of the two Philippine navy-manned boats managed to maneuver past the Chinese vessels and deliver supplies to the small contingent stationed on board a long-marooned but still actively commissioned warship, the BRP Sierra Madre, the task force said.

It was the latest flare-up in long-simmering territorial disputes in the South China Sea, one of the world’s busiest trade routes. The conflicts, which involve China, the Philippines, Vietnam, Malaysia, Taiwan and Brunei, are regarded as a potential flashpoint and have become a delicate fault line in U.S.-China rivalry in the region.

In early August, a Chinese coast guard ship used a water cannon against one of two Philippine supply boats to prevent it from approaching Second Thomas Shoal. The move, which was caught on video, outraged President Ferdinand Marcos Jr. and prompted the Department of Foreign Affairs in Manila to summon the Chinese ambassador to convey a strongly worded protest.

Washington reacted by renewing a warning that it is obligated to defend the Philippines as a treaty ally.

The Chinese Foreign Ministry accused Washington of “threatening China” by raising the possibility of activating the U.S.-Philippine mutual defense treaty. Beijing has repeatedly warned the U.S. not to meddle in regional territorial disputes.

Later in August, the Philippines again deployed two boats that got past the Chinese coast guard blockade and delivered supplies to the Filipino forces at Second Thomas Shoal. Two Philippine coast guard ships escorting the supply boats, however, were prevented by Chinese coast guard ships from maneuvering closer to the shoal. A U.S. Navy surveillance aircraft flew in circles in support of the Philippine vessels as the standoff continued for more than three hours.

A 2016 arbitration ruling set up under the 1982 U.N. Convention on the Law of the Sea invalidated Beijing’s claims on historical grounds to virtually the entire South China Sea. China refused to participate in the arbitration sought by the Philippines, rejected the decision and continues to defy it.

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Associated Press journalist Huizhong Wu contributed to this report from Bangkok.