HANOI, Vietnam (AP) — Vietnamese police broke up anti-China protests in two cities on Sunday and detained 20 people in the first such demonstrations since tensions between the communist neighbors flared anew over rival claims to the oil and gas-rich South China Sea.

Any sign of popular anger in tightly controlled Vietnam causes unease among the leadership, but anti-Chinese sentiment is especially sensitive. The country has long-standing ideological and economic ties with its giant neighbor, but many of those criticizing China are also the ones calling for political, religious and social freedoms at home.