North Korea's military vowed Wednesday to retaliate for anti-Pyongyang signs posted at front-line South Korean army units, as rare talks between the rivals on a stalled joint tourism project broke down.
North Korea also has been releasing water from a dam southward without prior notice since Monday night, Seoul officials said. A release on the same river caused a surge that killed six South Koreans in 2009.
The North's Korean People's Army issued its military warning via state media, promising "merciless military retaliatory measures" until South Korea apologizes and removes signs that it says "seriously hurt the dignity of the leadership" of North Korea.
The "hideous provocation" was "perpetrated only by hooligans who go wild like 'puppies knowing no fear of a tiger,'" an unidentified spokesman for the KPA's Supreme Command said.
Earlier Wednesday, an unidentified North Korean government spokesman warned of a "sacred war" against South Korea over the signs.
The threats follow a report Tuesday by South Korea's Hankyoreh newspaper that some South Korean army units near the border had set up anti-North Korea slogans in the wake of two deadly attacks blamed on North Korea last year.
The newspaper carried a photo showing a banner reading "Let's ram guns and swords into the chests of North Korean puppet soldiers!" hanging over the entrance of one army unit in Cheolwon, a town near the central portion of the demilitarized zone separating North and South Korea.
The newspaper said the unit also wrote on its walls such signs as "Let's hack the three Kims into pieces," a reference to late North Korea founder Kim Il Sung, his son and current leader Kim Jong Il, and grandson and heir-apparent Kim Jong Un.
South Korea's Defense Ministry confirmed the substance of the report, saying some army units have taken such measures to bolster their soldiers' mental toughness against North Korea.
North Korea has issued a series of warnings and made hostile statements aimed at the conservative government of South Korean President Lee Myung-bak.
The latest statements came as the two Koreas met at North Korea's scenic Diamond Mountain on Wednesday for talks on the North's seizure of South Korean assets there. However, the sides didn't have substantial discussions because of procedural differences and didn't set dates for any future meetings, according to Seoul's Unification Ministry.
Joint tours to the mountain were suspended in 2008 after a South Korean tourist was shot to death by a North Korean soldier. North Korea said she was in a restricted area and later confiscated or shut down South Korean-owned buildings and other facilities there.
South Korea's Land Ministry said a North Korean dam has been releasing about 1,000 tons of water per second over the past three days into a river flowing to South Korea. The release hasn't caused any damage in South Korea, it said.
The Unification Ministry said the North didn't inform South Korea of the water release.
In September 2009, the North also discharged a large amount of water into the Imjin River, killing six people.
The two Koreas are technically still at war because their 1950s conflict ended with a cease-fire, not a peace treaty.
Their animosity has deepened since North Korea allegedly torpedoed a South Korean warship in March last year. The North also shelled a South Korean border island in November. A total of 50 South Koreans were killed.
Last month, North Korea threatened to attack because South Korean troops were using photos of the three Kims as targets during firing drills. South Korea's Defense Ministry later told military units to stop using such photo targets, but it has no immediate plans to ask troops to stop using anti-North Korean signs, a ministry official said, speaking on condition of anonymity, citing office policy.