A Philippine official said Chinese coast guard ships chased and staged dangerous blocking manoeuvres on Monday against the Philippine coast guard and fishing vessels in the Scarborough Shoal.

The contested waters are a rich fishing atoll in the South China Sea off the northwestern Philippines.

Commodore Jay Tarriela said a Philippine coast guard ship managed to avoid being hit by a Chinese coast guard water cannon during the melee.

It’s the latest flare-up of long-simmering territorial disputes in the busy waterway, a key global trade route, where overlapping claims between China and the Philippines have escalated in recent years.

Vietnam, Malaysia, Brunei and Taiwan also lay claims to parts of the contested waters.

While chasing a Philippine coast guard vessel, a Chinese coast guard ship accidentally collided with a Chinese navy ship, Tarriela said.

The Chinese coast guard ship sustained “substantial damage” and the Philippine coast guard offered to provide help, including medical assistance, to the Chinese side, he said.

There was no immediate comment from Chinese officials on Tarriela’s statements.

Both China and the Philippines claim Scarborough Shoal and other outcroppings in the South China Sea.

China seized the shoal, which lies west of the main Philippine island of Luzon, in 2012 and has since restricted access to Filipino fishermen there.

A 2016 ruling by an international arbitration court found that most Chinese claims in the South China Sea were invalid but Beijing refuses to abide by it.