North Korean officials on June 25 warned of a "fire shower" of nuclear retaliation, if provoked by the United States. The U.S. military has been following a North Korean cargo ship, suspected of carrying illicit weapons, for a week. North Korea says it would be an act of war if the U.S. military boards one of its ships.
North Koreans flooded Kim Il Sung Square Thursday in a show of defiance against the West. The rally marked the day North Korea invaded South Korea in 1950.
Senior government official Pak Pyong Jong threatened war, if North Korea is provoked.
"Our revolutionary armed forces will deal an annihilating blow that is unpredictable and unavoidable, to any 'sanctions' or provocations by the U.S, and will mercilessly destroy the stronghold of aggression of the enemy," he said.
Pyongyang has toughened its rhetoric against Washington since President Obama promised to defend South Korea with a "nuclear umbrella" earlier this month.
A U.S. Navy destroyer has been tracking a North Korean ship suspected of smuggling missiles and illicit weapons technology. The U.S. military has not said if it will board and inspect the Kang Nam.
A Japanese newspaper says North Korea is preparing to launch a long-range ballistic missile towards Hawaii in early July.
After North Korea conducted an underground nuclear test in May, the U.N. Security Council and the Obama administration imposed sanctions on Pyonyang.
"After the nuclear test conducted by North Korea, I spoke to U.S. President Obama on the phone and he said that the U.S. will 100 percent ensure Japan's security in terms of nuclear deterrence," Japanese Prime Minister Taro Aso said.
Aso met with U.S. Defense Department official Michele Flournoy on June 25, and was reassured.
In South Korea, protesters also observed the anniversary of the Korean War with a demonstration against North Korea's latest threats.