Protesters called for China to stop entering Vietnamese waters in the South China Sea.
China is angry over the United States` support of Southeast Asian countries.
China will boost its coastal forces by adding ships and 6,000 personnel by 2020, state media said.
China has quarrelled with both Vietnam and the Philippines in recent weeks over maritime claims.
Day in Pics: 29th December
Showbiz World - December 29, 2014
Stars celebrate Christmas