North Korea has delivered a drumbeat of war threats and ominous announcements since March 7, when the United Nations Security Council imposed sanctions against it for conducting a nuclear test in February. Here are the most significant:
March 7: Before the UN vote, a spokesman for Pyongyang's foreign ministry says North Korea will exercise its right for a pre-emptive nuclear attack against the United States.
March 8: The North says it will cancel a hotline and a nonaggression pact with rival South Korea.
March 11: Following through on a threat made the previous week, Pyongyang says it has nullified the 60-year-old armistice ending the Korean War. South Korea and the UN say the North cannot end the pact unilaterally.
March 12: North Korea state media report that the country's leader, Kim Jong Un, urged front-line troops to be on "maximum alert" and warned that "war can break out right now."
March 20: Coordinated cyberattacks in South Korea knock out computers and servers at three major TV networks and three banks. The source of the attacks remains under investigation but North Korean involvement is suspected. A week later, organizations of North Korean defectors say their systems were also attacked.
March 22: The North condemns a UN resolution approving a formal investigation into its suspected human rights violations and says it will ignore the measure.
March 27: North Korea cuts a military hotline to its Kaesong industrial complex, which is jointly run with the South and is the last major example of inter-Korean cooperation. Operations at the complex continued.
March 29: Kim convenes an "urgent operation meeting" of senior generals just after midnight, signs a rocket preparation plan and orders his forces on standby to strike the US mainland, South Korea, Guam and Hawaii. State media quote him as saying that "the time has come to settle accounts with the US imperialists."
March 30: North Korea warns that "inter-Korean relations have naturally entered the state of war," and that it would retaliate against any US and South Korean provocations without notice. It says in a statement that provocations "will not be limited to a local war, but develop into an all-out war, a nuclear war."
March 31: The Central Committee of the ruling Workers' Party warns that North Korea's nuclear weapons are "the nation's life" and will not be traded even for "billions of dollars."
April 2: North Korea's atomic energy department says it will restart facilities at its main Nyongbyon nuclear complex, including a plutonium reactor and a uranium enrichment plant. The US says it would be "extremely alarming" if Pyongyang follows through.
April 3: North Korea bars South Koreans from going to their jobs at the Kaesong industrial complex, and also closes the border to trucks carrying raw materials for the factories.