North Korea has stepped up its anti-Seoul loudspeaker broadcasts in the border regions amid escalating tensions. Pyongyang's move is a countermeasure against South Korea, which has also been carrying out loudspeaker broadcasts critical of the Kim Jong-un regime.

Pyongyang's retaliation has also intensified in the wake of the US and South Korea deploying a powerful B-52 bomber, which flew above the Korean peninsula in a muscle-flexing exercise. The loudspeaker broadcasts are often considered psychological warfare in North Korea, which has tight control over how information is passed across the country.

"The North initially operated its own loudspeakers at two locations and has now expanded to several locations. In fact, the anti-South loudspeaker broadcasts appear to be coming from every location where we are broadcasting," a South Korean government source told Yonhap news agency.

Most of the North's broadcasts heap praise on Kim's regime and contain domestic propaganda messages. Local reports suggest the messages are not clearly audible from the South Korean side of the border, which is the most-militarised frontier in the world. Either due to power issues or low quality loudspeakers, the broadcasts, which also include harsh messages on South Korean President Park Geun-hye, were not heard clearly, according to reports.

North Korea sees its neighbour's loudspeaker propaganda as a provocative move since any information from the outside world to the isolated country is heavily censored. South Korea has swiftly resumed broadcasts after the North conducted its fourth nuclear test, claiming it was a hydrogen bomb detonation. Today (11 January) marked the fourth consecutive day of broadcasts. South Korean military forces in the area have also been kept on high alert over possible military action from the North.