China said Tuesday that a Vietnamese protest over who controls islands in the South China Sea has damaged bilateral relations.
On Sunday, several hundred Vietnamese staged a rare public demonstration to protest China's effort to claim control of two disputed island chains there.
The protesters were supporting the government's position that Vietnam has sovereignty over the Spratly and Paracel islands, a contentious issue between Vietnam and China for years.
The demonstrators, mostly university students, gathered near the Chinese Embassy in Hanoi and chanted "Down with China" and "Long Live Vietnam."
Police let the demonstration continue for about an hour before breaking it up.