Changbai county, in north-east China, is renowned for its seafood and mountain views. It is also so close to North Korea that residents felt the tremors from the hermit kingdom’s most recent underground nuclear test, conducted in September.

With the escalating threat of military conflict between the US and Kim Jong Un’s regime, local officials and residents in Changbai fear more serious scenarios that could force millions of people from their homes on both sides of the border.

In an official company document that went viral on Chinese social media on Thursday and seen by the Financial Times, the Changbai branch of China’s largest mobile phone company said it had tested signal strength at five sites designated by local authorities as potential “refugee settlement points”.