The incident is a dramatic outburst of a simmering controversy that has major global ramifications, as China is claiming sovereignty over one of the most important shipping lanes in the world. Chinese officials denied responsibility for the collision, which took place Thursday. “The Vietnamese boat refused to leave and suddenly veered sharply towards the Chinese vessel,” Chinese Foreign Ministry spokeswoman Hua Chunying said Friday. “Despite its best efforts to keep clear, the Coast Guard vessel was struck at the bow. The Vietnamese fishing boat then took in water and sank.”