To the alarm of the Vietnamese government, China is apparently building a surface-to-air missile base 20 kilometres from its border with Vietnam, as a long-term precaution and near-term warning to neighbouring countries, observers say. China has solidified its maritime claims over the past decade by reclaiming land to build up tiny islets for military use. PetroVietnam is proposing new natural gas exploration projects in the South China Sea, so the nearby missile base could be a “warning from China,” said Dr Collin Koh, a maritime security Research Fellow at RSIS.