China and the Philippines accused each other of ramming their ships in a disputed area of the South China Sea on Saturday, the latest in an escalating series of clashes in the vital waterway.

China’s coast guard said a Philippine ship, “illegally stranded” at the Sabina Shoal, had lifted anchor and “deliberately rammed” a Chinese vessel, while the Philippine coast guard said a Chinese vessel had “intentionally rammed” one of Manila’s ships.

Beijing claims almost the entire South China Sea, including parts claimed by the Philippines, Brunei, Malaysia, Taiwan and Vietnam. Portions of the waterway, where $3 trillion worth of trade passes annually, are believed to be rich in oil and natural gas deposits, as well as fish stocks.

The Permanent Court of Arbitration in 2016 found China’s sweeping claims had no legal basis, a ruling Beijing rejects.

Liu Dejun, a spokesperson for China’s coast guard, called on the Philippines in a statement to withdraw immediately from the shoal.

“The Chinese coast guard will take the measures required to resolutely thwart all acts of provocation, nuisance and infringement and resolutely safeguard the country’s territorial sovereignty and maritime rights and interests,” Liu said.

Philippines Coast Guard spokesperson Jay Tarriela told a press conference that the Chinese Coast Guard had ignored collision regulations and carried out dangerous maneuvers, resulting in damage but that no injuries had been reported.

The shoal is within the Philippines’ 200-nautical mile exclusive economic zone.