NEW DELHI: Is China building a surface-to-air missile base close to the Vietnam border? On Thursday, Vietnam's foreign ministry, responding to questions after an NGO, South China Sea News, tweeted satellite images of a possible missile base, said it would have to investigate.

"We will verify the information," foreign ministry spokeswoman Le Thi Thu Hang said at a press meet, according to local media reports. The satellite images appeared to show a missile base being almost completed just 20km away from the Vietnam border. This is reportedly being done in Ningming county of China's Guanxi province.

The NGO also said a helicopter base was being built a little further inland. The images showed the presence of radars and at least six launchers along a military runway.

This comes a week after China announced that its air force bombers had conducted a mock attack on the USS Theodore Roosevelt strike group in the South China Sea.