North Korea today threatened to attack sites in South Korea if Seoul carries out its threat to start cross-border propaganda broadcasts.Pyongyang's official news agency said the North Korea's military renewed its earlier threats of a strike in a message to the South's armed forces. The North's military said, loudspeakers and other sites will face a physical strike from their army if South Korea launches its propaganda campaign. It also described comments by the South's defence minister last week about a possible resumption of propaganda broadcasts as a declaration of war and grave military provocation. Last week, South Korea's Defence Minister Kim Tae-Young said the speakers would be switched on and the leaflets would be launched in response to any fresh cross-border provocation.The two sides reached a deal in 2004 to halt their cross-border government-level propaganda war. But the South made preparations to restart it after accusing the North of sinking one of its warships in March, a charge it denies.