She did not confirm the boat collisions . China has started drilling for oil in a part of the South China Sea also claimed by Vietnam . Vietnam claims Chinese fishermen have made violent attacks on Vietnamese vessels . Chinese fishermen detained by Vietnamese authorities in a separate dispute . This could escalate into armed conflict , analyst says .
China has started drilling for oil in a part of the South China Sea also claimed by Vietnam . Vietnam claims Chinese fishermen have made violent attacks on Vietnamese vessels . Chinese fishermen detained by Vietnamese authorities in a separate dispute . This could escalate into armed conflict , analyst says .