SEOUL: South Korea on Tuesday vowed a stern response if North Korea acts on threats to strengthen its military posture along the border, which have fuelled tensions on the Korean Peninsula.

In a statement, Seoul's Defence Ministry expressed grave concern over Pyongyang's threats to deploy additional tactical strike weapons along the border and resume loudspeaker broadcasts towards the South.

The escalation and exchange of threats has raised the possibility of clashes along the heavily armed border and undercuts diplomatic gains made by South Korean President Lee Jae Myung soon after he took office.

The ministry said South Korea's broadcasts and warning shots near the Military Demarcation Line (MDL) were a "legitimate defensive measure" aimed at preventing incursions and forcing North Korean troops who crossed the line to withdraw.