Seoul: North Korea has increased the number of troops at some forward-deployed units as South Korea readied to restart propaganda loudspeaker broadcasts in retaliation for the North`s nuclear test, Yonhap news agency reported on Friday.
The broadcasts, which North Korea considers insulting, were scheduled to start at noon local time (0300 GMT) after Pyongyang conducted a fourth nuclear test on Wednesday.
Seoul said the test was a "grave violation" of an August agreement that ended earlier loudspeaker broadcasts. The Yonhap report cited an unidentified defence official.
The South has raised its military alert to the highest level in areas near the loudspeakers, and has also stepped up its cyber security level.
South Korea`s Unification Ministry said earlier that it was not yet considering shutting down the Kaesong industrial complex run jointly with the North, located north of the heavily militarised border.
The ministry also said there had been no government decision on what North Korea needed to do to end the propaganda broadcasts.
The August agreement ended an armed standoff that had been triggered by earlier loudspeaker broadcasts.