Punching their fists into the air and shouting “Let’s crush them!” some 100,000 North Koreans packed Pyongyang’s main square Thursday for an anti-U.S. rally as the communist regime promised a “fire shower of nuclear retaliation” for any American-led attack.

Several demonstrators held up a placard depicting a pair of hands smashing a missile with “U.S.” written on it, according to footage taken by APTN in Pyongyang on the anniversary of the day North Korean troops charged southward, sparking the three-year Korean War in 1950.

North Korean troops will respond to any sanctions or U.S. provocations with “an annihilating blow,” one senior official vowed – a pointed threat as an American destroyer shadowed a North Korean freighter sailing off China’s coast, possibly with banned goods on board.

A new U.N. Security Council resolution passed recently to punish North Korea for conducting an underground nuclear test in May requires U.N. member states to request inspections of ships suspected of carrying arms or nuclear weapons-related material.

In response to the sanctions, the North pulled out of nuclear talks and has ramped up already strident anti-American rhetoric. And the isolated regime may now be moving to openly flout the resolution by dispatching a ship suspected of carrying arms to Myanmar.

While it was not clear what was on board the North Korean-flagged Kang Nam 1, officials have mentioned artillery and other conventional weaponry. One intelligence expert suspected missiles.

The U.S. and its allies have made no decision on whether to request inspection of the ship, Pentagon press secretary Geoff Morrell said Wednesday in Washington, but North Korea has said it would consider any interception an act of war.

If permission for inspection is refused, the ship must dock at a port of its choosing so local authorities can check its cargo. Vessels suspected of carrying banned goods must not be offered bunkering services at port, such as fuel, the resolution says.

A senior U.S. defense official said the ship had cleared the Taiwan Strait. He said he didn’t know whether or when the Kang Nam may need to stop in some port to refuel, but that the Kang Nam has in the past stopped in Hong Kong’s port.

Another U.S. defense official said he tended to doubt reports that the Kang Nam was carrying nuclear-related equipment, saying information seems to indicate the cargo is banned conventional munitions. Both officials spoke on condition of anonymity in order to talk about intelligence.

North Korea has been locked in a tense standoff with Washington and other regional powers over its nuclear program. In April, the regime launched a rocket widely seen as a cover for a test of long-range missile technology – a move that drew U.N. Security Council condemnation.

The North responded by abandoning six-nation disarmament talks and threatening to carry out nuclear tests and fire intercontinental ballistic missiles. The North is believed to be developing a long-range missile designed to strike the U.S. but experts say it has not figured out how to mount a bomb onto the missile.

On Thursday, Pyongyang vowed to enlarge its atomic arsenal and warned of a “fire shower of nuclear retaliation” if provoked by the U.S.

North Korea’s “armed forces will deal an annihilating blow that is unpredictable and unavoidable, to any ‘sanctions’ or provocations by the US,” Pak Pyong Jong, first vice chairman of the Pyongyang City People’s Committee, told the crowd gathered for the Korean War anniversary rally.

(Source: CBS News)