MANILA, Philippines (AP) — The Philippine military on Sunday condemned a Chinese coast guard ship’s “excessive and offensive” use of a water cannon to block a Filipino supply boat from delivering new troops, food, water and fuel to a Philippine-occupied shoal in the disputed South China Sea.

The tense confrontation on Saturday at the Second Thomas Shoal was the latest flare-up in the long-seething territorial conflicts involving China, the Philippines, Vietnam, Malaysia, Taiwan and Brunei.

The disputes in the South China Sea, one of the world’s busiest sea lanes, have long been regarded as an Asian flashpoint and a delicate fault line in the rivalry between the United States and China in the region.

Philippine navy personnel on board two chartered supply boats were cruising toward Second Thomas, escorted by Philippine coast guard ships, when a Chinese coast guard ship approached and used a powerful water cannon to block the Filipinos from the shoal that China also claims, according to Philippine military and coast guard officials.

The Chinese ship’s action was “in wanton disregard of the safety of the people on board” the Philippine navy-chartered boat and violated international law, including the 1982 U.N. Convention on the Law of the Sea, said the Armed Forces of the Philippines, which did not say if any of its sailors were injured.

The “excessive and offensive actions against Philippine vessels” near the shoal prevented one of the two Filipino boats from unloading supplies needed by Filipino troops guarding the shoal onboard a long-marooned Philippine navy ship, the BRP Sierra Madre, the Philippine military said in a statement.

It called on the Chinese coast guard and China’s central military commission “to act with prudence and be responsible in their actions to prevent miscalculations and accidents that will endanger peoples’ lives.”

The Department of Foreign Affairs in Manila did not immediately issue any reaction but has filed a large number of diplomatic protests over increasingly hostile actions by China in recent years. Chinese government officials did not immediately comment on the incident.

China has long demanded that the Philippines withdraw its small contingent of naval forces and tow away the actively commissioned but crumbling BRP Sierra Madre. The navy ship was deliberately marooned on the shoal in 1999 and now serves as a fragile symbol of Manila’s territorial claim to the atoll.

Chinese ships had blocked and shadowed navy vessels delivering food and other supplies to the Filipino sailors on the ship in the shoal, which Chinese coast guard ships and a swarm of Chinese fishing boats — suspected to be manned by militias — have surrounded for years.

While the U.S. lays no claims to the South China Sea, it has often lashed out at China’s aggressive actions and deployed its warships and fighter jets in patrols and military exercises with regional allies to uphold freedom of navigation and overflight, which it says is in America’s national interest.

China has warned the U.S. to stop meddling in what it calls a purely Asian dispute and has warned of unspecified repercussions.

Additionally, Beijing has criticized a recent agreement by the Philippines and the U.S., which are longtime treaty allies, allowing American forces access to additional Filipino military camps under a 2014 defense agreement.

China fears the access will provide Washington with military staging grounds and surveillance outposts in the northern Philippines across the sea from Taiwan, which Beijing claims as its territory, and in Philippine provinces facing the South China Sea, which Beijing claims virtually in its entirety.