North Korea on Tuesday urged foreigners living in South Korea to consider evacuating, saying there was a risk of "thermo-nuclear war" breaking out on the Korean peninsula.
The United States and South Korea have drawn up plans for a measured tit-for-tat response to North Korean actions, which will be limited in order to prevent an escalation to broader war.
North Korea appears to be preparing for a fourth nuclear test, South Korea said Monday, following intelligence reports of heightened activity at its main atomic test site.
The United States is pressuring China's new President Xi Jinping to crack down on the regime in North Korea or face an increased US military presence in the region.
Foreign diplomats in Pyongyang huddled on Saturday to discuss a North Korean evacuation advisory as concerns grew that the isolated state was preparing a missile launch at a time of soaring nuclear tensions.
The United States said it was taking "all necessary precautions" after North Korea rang fresh alarms in an escalating crisis by moving a medium-range missile Thursday to its east coast.
Much like his father Kim Jong-Il, North Korea's new young leader Kim Jong-Un is viewed by much of the outside world with a heady mix of incomprehension, ridicule and fear.
North Korea threatened Thursday to pull its 53,000 workers from the Kaesong joint industrial zone with South Korea and close the complex, a day after it blocked access for South Korean personnel.
The United States vowed to defend itself and its regional allies Tuesday after North Korea again stepped up its warlike rhetoric and the UN warned that the crisis could spin out of control.
North Korea blocked South Korean access to a key joint industrial zone Wednesday, matching its angry rhetoric with action as Washington condemned Pyongyang's "dangerous, reckless" behaviour.
The UN General Assembly on Tuesday passed the first treaty regulating the conventional arms trade in an attempt to bring transparency and protection of human rights to the often murky industry.
South Korea's new president on Monday promised a strong military response to any North Korean provocation after Pyongyang announced that the two countries were now in a state of war.
The UN General Assembly is expected to adopt the first global treaty on the conventional arms trade Tuesday after the 193 member states failed to reach consensus on it last week.
Pope Francis prayed for a "political solution" in Syria and for "reconciliation" on the Korean peninsula in his first Easter Sunday message in front of a crowd in St Peter's Square.
South Korean President Park Geun-Hye vowed "strong retaliation" Monday to any provocation by North Korea after Pyongyang declared it was formally at war with Seoul.
North Korea on Saturday declared it had entered into a "state of war" with South Korea and warned Seoul and Washington that any provocation would swiftly escalate into an all-out nuclear conflict.