North Korea has vowed to make the country’s borders with South Korea “impregnable”, as the powerful sister of dictator Kim Jong Un threatened Seoul with an “overwhelming” military response to any perceived provocation.

Kim Yo Jong , visited the border between the two countries alongside marshal Pak Jong-chon, a senior adviser to the North Korean military, where the two inspected work to fortify defences, the state-run Korean Central News Agency reported on Wednesday.

Ms Kim directed troops there to take “prompt and resolute action” in the face of any threat.

The border visit came after the South Korean military vowed to take its own “decisive” action in response to North Korea’s provocations, after Pyongyang threatened to deploy additional tactical strike capability along its borders.

Ms Kim has also threatened to resume loudspeaker propaganda broadcasts towards the South.

Kim Yo Jong made the threats to state-owned media on Monday (Reuters)

She accused Seoul of escalating tensions with warning shots…