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: 19th September
Showbiz World - September 19, 2014
iPhone6 fever grips the world