North Korea marked on Friday the third anniversary of an artillery attack on a South Korean island with a vow to respond to what it called any similar provocation with a strike on the South Korean presidential compound.
North Korea fired scores of artillery shells at South Korea's Yeonpyeong island on Nov. 23, 2010, killing four people including two civilians in one of the heaviest attacks on its neighbour since the Korean War ended in 1953.
It took many months for tension between the rivals to ease but it spiked again in March this year, during annual joint military exercises by the South and the United States. The North, which has conducted three nuclear tests, threatened nuclear attacks against the allies.
The hostility has cooled since then but the bellicose message on the anniversary of the island attack is a reminder of the unpredictability of the North.
"Three years ago the retaliatory blow was confined to the Yeonpyeong island only but this time Chongwadae and other bases of the puppet forces will be put within striking range," said a spokesman for the North's military, according to the North's KCNA news agency.
The South Korean presidential compound in Seoul is known as Chongwadae in Korean and the Blue House in English.
The North has threatened to attack Seoul before but it is seen as highly unlikely as doing so would almost certainly trigger all-out war with the South and the United States which, under a defence treaty, stations 28,500 troops in the South.
In 2010, the North said it was provoked into attacking Yeonpyeong, which is off the peninsula's west coast, because of a live-fire South Korean exercise in the area that dropped shells in its territorial waters.
Earlier in 2010, the North was widely blamed for infiltrating a submarine across the border and sinking a South Korean navy ship with a torpedo killing 46 sailors.
North Korea denied that.
South Korea has strengthen its military presence in the area since 2010 with the deployment of GPS-guided missiles. It has vowed to strike back if hit again.
The maritime border, called the Northern Limit Line, separating the waters off the west coast, was unilaterally drawn at the end of the 1950-53 Korean War by the U.N. forces that fought for the South.
The North does not recognise the line and has demanded a redrawing of the demarcation. Naval clashes do erupt every now and then and sailors on both sides have been killed.