Here is a brief history of clashes between the two Koreas since the 1950-1953 war, which ended in an armistice rather than a formal peace treaty:
January 21, 1968: North Korean commandos stage a raid on Seoul’s presidential Blue House in an attempt to assassinate President Park Chung-Hee.
They are stopped just 800 metres (yards) away. All 32 are killed or captured in subsequent days.
August 15, 1974: North Korean agent fires at Park during a speech. He misses but the shot kills the president’s wife. Park continues his speech.
October 9, 1983: The North’s agents blow up a landmark in Burma (now Myanmar) just before the visiting South Korean President Chun Hoo-Hwan is set to arrive. Four South Korean cabinet ministers and 16 others are killed.
November 29, 1987: All 115 people on board are killed when a bomb planted by the North’s agents explodes on a South Korean airliner.
September 1996: A North Korean submarine lands commandos on the South Korean coast, prompting a huge manhunt. Twenty-four infiltrators are shot dead including 11 by their own hand, one is captured and one unaccounted for.
June 15, 1999: A clash breaks out along the Yellow Sea border, the first naval battle since the Korean War. A North Korean boat with an estimated 20 sailors aboard is sunk.
June 29, 2002: A South Korean ship is sunk and six sailors killed in another Yellow Sea clash, while Seoul is co-hosting the football World Cup. An estimated 13 North Koreans die.
November 10, 2009: Navies of the two sides exchange fire near the Yellow Sea border. Seoul officials say a North Korean patrol boat retreated in flames but its casualties are unknown. No South Koreans are hurt.
March 26, 2010: An unexplained explosion hits the Cheonan, a 1,200-tonne South Korean corvette, near the disputed border and the warship breaks in two. A total of 58 sailors are rescued but 46 die.
May 20, 2010: A report by a multinational investigation team says the Cheonan was sunk by a torpedo launched from a North Korean submarine.
May 24, 2010: South Korea suspends trade with the North and bans its ships from Seoul’s waters. The White House says the sanctions are “entirely appropriate” as President Barack Obama orders the US military to work closely with South Korea.
Oct 29, 2010: North and South Korean troops exchange fire across their border, cranking up tensions before the G20 summit of world leaders in Seoul.
Nov 23, 2010: North Korea fires artillery shells onto a South Korean border island, prompting an exchange of fire with southern troops along with casualties and property damage, officials and reports said.