SEOUL - North Korea's military on June 3 threatened retaliation against South Korea unless Seoul punishes troops who used pictures of Pyongyang's ruling dynasty as rifle-range targets.
The South's defense ministry said earlier this week it had ordered the army reservists to discontinue the practice and to use normal targets.
But the North's military general staff called for an apology and stern punishment for those involved.
The North's regular armed forces and reservists would "escalate the practical and overall retaliatory military actions till the puppet authorities have taken measures to punish the prime movers... and make an apology for them," said a military statement on the official news agency.
Several Seoul media outlets published pictures of targets depicting the North's leader Kim Jong-Il, his late father and founding president Kim Il-Sung and Kim Jong-Il's youngest son and heir apparent Kim Jong-Un.
"The recent hideous provocation is a never-to-pardoned treason," said the North's statement, which did not elaborate on the threatened retaliation.
It called on the South's "puppet authorities" - a reference to President Lee Myung-Bak's government - to "apologize to the nation for the evil deeds committed by traitor Lee Myung-Bak and the puppet army hooligans and take a responsible step for their prevention."
Cross-border relations have been icy for more than a year, since the South accused the North of sinking one of its warships and imposed trade sanctions.
The North denies involvement in the March 2010 sinking. But it shelled a South Korean border island last November, killing four people including two civilians.
In an abrupt change of tack in January, the North began calling for peace and dialogue. But this week it announced it would no longer deal with Lee's government.
On June 1 it said it had rejected a South Korean proposal to hold a series of three summits designed to ease tensions on the peninsula.
South Korea confirmed it had held a secret meeting with the North in Beijing in May. But it said the main purpose was to try to persuade the North to apologize for the two border incidents and to promise no recurrence.
Seoul says its neighbor must take responsibility for the incidents before there can be any serious peace dialogue.
Some analysts believe the North will not mount further attacks while it is seeking U.S. food aid and preparing for a major political anniversary next year.
But others say its decision to disclose the diplomatic contacts is worrying. Seoul critics cited Lee's alleged double-dealing in seeking summits while publicly maintaining a tough line with Pyongyang.
But U.S. academic Marcus Noland said the disturbing aspect "is not Lee Myung-Bak's alleged hypocrisy but rather North Korea's recklessness.
"One has to assume that this behavior is connected to North Korea's internal political machinations and could augur further provocations in the future," he wrote in a blog posting.
Several U.S. and South Korean officials have warned of heightened uncertainty as Kim puts in place a succession plan involving his son.