China and the Philippines on Monday defended their claims to a disputed reef in the South China Sea, after Manila accused Beijing of seeking to “intimidate and harass” with a state media report that suggested the area had been seized.

Philippine officials say a mission visited Sandy Cay Reef in disputed South China Sea and unfurled the national flag.

Both countries have planted flags on a collection of sand bars, extending the clash over the area between Beijing and Manila, a U.S. ally.