Two countries were involved in a second incident at the controversial Second Thomas Shoal this month.

Manila has accused the Chinese coast guard of firing water cannons at one of its supply boats in the latest incident between the two countries in the disputed South China Sea.

The Philippine military said Saturday morning’s confrontation lasted nearly an hour and occurred as it attempted to resupply a small garrison of sailors aboard the sunken Sierra Madre off Second Thomas Shoal.

The shoal, known in the Philippines as Ayungin, has been the site of several similar standoffs in the last few months. It lies about 200 kilometers (124 miles) from the western Philippine island of Palawan and more than 1,000 kilometers (621 miles) from China’s southern island of Hainan.

The military released a video clip showing a white ship marked “China Coast Guard” crossing the bow of a gray vessel it identified as the Philippine supply ship Unaizah on May 4 and firing its water cannons.

“The supply boat UM4 suffered severe damage at around 08:52 a.m. (00:52 GMT) as the CCG ships continued to fire water cannons,” the military said in a statement, without elaborating on the damage.

A Philippine Coast Guard escort ship later reached the damaged boat “to provide assistance,” the military said.

Gan Yu, a spokesman for the Chinese Coast Guard, said that the Philippine convoy “forcibly entered the area despite the Chinese side’s repeated warnings and route controls,” adding that the Chinese “carried out control, obstruction and evacuation in accordance with the Law”.

China claims almost the entire South China Sea, although an international court found in 2016 that the nine-dash line on which it based its claim was without merit. The Philippines claims maritime areas around its coasts, as do Brunei, Malaysia and Vietnam. The self-governing island of Taiwan is also a plaintiff.

Manila has revived and expanded its military relations with the United Statesa long-time ally as the situation has become more tense.

The United States does not claim ownership of the strategic waters but has sent naval ships on transit missions through the waterway in what it calls “freedom of navigation” operations that have been criticized by China.

US Secretary of State Antony Blinken visited the Philippines last week and stressed that the US commitment to Manila was “ironclad”.

Two days after that visit, the Chinese coast guard also attempted to expel Filipino scientists who landed on two islands near Scarborough Shoal, a disputed rocky outcrop in the South China Sea Beijing captured the Philippines after a months-long standoff in 2012.

The Unaizah May 4 returned to sea after a water cannon attack by the Chinese Coast Guard off Second Thomas Shoal earlier this month. She was escorted by two Philippine Coast Guard ships and two Philippine Navy ships, a Philippine military statement said.

Commodore Jay Tarriela, Philippine Coast Guard spokesman for South China Sea issues, said in a separate statement that one of the escort ships, the BRP Cabra, was “obstructed and encircled” by three Chinese Coast Guard ships and other vessels early Saturday.

As a result, Cabra was “isolated from the supply boat due to the irresponsible and provocative behavior of the Chinese naval forces,” he added.

The Chinese side is showing “disregard” for the Convention on International Regulations for the Prevention of Collisions at Sea (COLREGS), the statement said.

The Sierra Madre ran aground in 1999 and the troops living on the warship need regular supplies of food, water and other essentials.