President Ferdinand Marcos Jr. said Sunday the Philippines "will not be intimidated" by anyone after a violent clash between the country's navy and the Chinese coast guard in the South China Sea.

The confrontation took place Monday off Second Thomas Shoal as the Chinese sailors foiled an attempt by Philippine forces to resupply marines stationed on a derelict warship that was deliberately grounded atop the disputed shoal in 1999 to assert Manila's territorial claims.

It was the latest and most serious incident in a series of escalating confrontations between Chinese and Philippine ships in recent months as Beijing steps up efforts to push its claims to nearly all of the strategically located waterway.