SEOUL: The Democratic People's Republic of Korea (DPRK) vowed yesterday to enlarge its atomic arsenal and warned of a "fire shower of nuclear retaliation" in the event of a US attack, as the country marked the 1950 outbreak of the Korean War.

The anniversary came as the US Navy followed a DPRK ship suspected of carrying weapons in violation of a UN resolution punishing Pyongyang's May 25 nuclear test, and as anticipation mounted that the DPRK might test-fire short- or mid-range missiles in the coming days.

President Barack Obama extended US economic sanctions against the DPRK for another year on Wednesday, saying the DPRK's possession of "weapons-usable fissile material" and its proliferation risk "continue to pose an unusual and extraordinary threat" to the United States, according to the White House website.