China and the Philippines traded accusations over a collision in disputed waters of the South China Sea as Chinese vessels blocked Philippine boats supplying forces there on Sunday in the latest of a series of maritime confrontations.

The two countries have had numerous run-ins in the South China Sea in recent months, especially near the disputed Second Thomas Shoal, part of the Spratly Islands.

The Philippines has sent supplies to troops stationed on a rusted World War II-era transport ship used as an outpost on the shoal, prompting China’s coast guard to repeatedly deploy vessels to block the resupply missions.

In the incident early on Sunday, China’s coast guard said there had been a “slight collision” between one of its ships and the Philippine boat while the coast guard was “lawfully” blocking the boat from transporting “illegal construction materials” to the warship.

Manila responded by condemning “in the strongest degree” the “dangerous blocking maneuvers” of the Chinese vessel.

China’s “dangerous, irresponsible and illegal actions” were “in violation of Philippine sovereignty, sovereign rights and jurisdiction,” Manila’s Task Force for the West Philippine Sea said in a statement.

Beijing claims sovereignty over almost the entire South China Sea, including parts of the exclusive economic zones of Brunei, Indonesia, Malaysia, the Philippines and Vietnam. The Permanent Court of Arbitration in 2016 said China’s claims had no legal basis.

“China has maintained great restraint and patience on the issue,” the Chinese foreign ministry said on Sunday.

China has long maintained intensive communication with Manila, which has, however, disregarded China’s goodwill, the ministry said in a statement.

China will continue to take the necessary measures in accordance with domestic and international laws to safeguard its territorial sovereignty, it said.

The U.S. sided with the Philippines, offering support to its ally. In a statement on Sunday, the State Department said China’s actions amounted to repeated “harassment” in the South China Sea, and that they were “dangerous and unlawful.”

The Canadian and Japanese embassies in Manila also expressed support for the Philippines and alarm over the collision. The European Union’s ambassador, Luc Veron, said: “These incidents, their repetition and intensification are dangerous and very disturbing.”

Manila’s relations with Beijing have soured under President Ferdinand Marcos Jr., who has strengthened military engagement with Washington since taking office last year. The Pentagon said in May it would protect the Philippines if its coast guard came under attack “anywhere in the South China Sea.”

Last week, the Philippine military demanded China stop its “dangerous and offensive” actions after a Chinese navy ship shadowed and attempted to cut off a Philippine navy vessel conducting a resupply mission.

Sunday’s collision occurred during a routine resupply mission of a boat contracted by the Philippine armed forces, Manila said.

In another incident during the same resupply mission, it said a Philippine coast guard vessel’s port side was bumped by a Chinese maritime militia vessel.

The actions of the Chinese coast guard vessel “imperiled the safety of the crew” of the Philippine boat, the task force said.

China’s coast guard said in a statement that the Philippine vessel had ignored repeated warnings, crossed the bow of the Chinese ship and “deliberately provoked trouble,” causing the collision.

“The Philippines behavior seriously violates the international rules on avoiding collisions at sea and threatens the navigation safety of our vessels,” the coast guard said.

Manila grounded the BRP Sierra Madre warship in 1999 as part of its sovereignty claim to the Second Thomas Shoal, which lies within its 200-mile exclusive economic zone.