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.

The competing claims are reigniting tensions in the South China Sea and coincide with joint military drills between the U.S. and the Philippines.