SEOUL (AFP) - North Korea warned Thursday that dark clouds of nuclear war are gathering over the peninsula and vowed to strengthen its atomic arsenal as it marked the anniversary of the 1950-1953 conflict. Rodong Sinmun, newspaper of the ruling communist party, accused the United States and its ally South Korea of trying to provoke another war with their pledge of a US nuclear umbrella over the South. A touch-and-go situation has been created on the Korean peninsula... with dark clouds of a nuclear war gathering as the hours tick by, it said in a lengthy commentary marking the anniversary, carried by the official news agency. The paper said a new war could break out any time and the North would continue to strengthen its nuclear arsenal. As long as the US hostile policy continues, we will never give up our nuclear deterrent and even strengthen it, Rodong said. The conflict began with a North Korean invasion on June 25, 1950. It ended with an armistice rather than a peace treaty, leaving the communist North and capitalist South still technically at war. North Korea marked the day of the struggle against US imperialism with a mass rally of 100,000 people in Pyongyang, the Norths KCNA news agency said, although ailing leader Kim Jong-Il was not among those reported to have attended. The US headed a United Nations force which fought for the South against North Korean and Chinese troops. Of late the US has become evermore frantic in its moves to stifle the DPRK (North Korea) over its satellite launch for peaceful purposes and nuclear test for self-defence, Pak Pyong Jong, first vice chairman of the Pyongyang City Peoples Committee, said in a speech at the rally, KCNA reported. At the present stage where the army and people of the DPRK are standing in all-out confrontation with the US they will counter 'sanctions with retaliation and all-out war with all-out war in order to protect the dignity of the nation and the sovereignty of the country. International tensions have grown since Pyongyangs long-range rocket launch in early April and its nuclear test in late May which resulted in new UN sanctions. The North has also fired short-range missiles, renounced the truce in force on the peninsula and repeatedly warned of possible war. Cross-border relations have soured since a conservative government took office in Seoul in February last year with a firmer policy towards the North. At a US-South Korean summit in Washington last week, Washington reaffirmed its commitment to provide the South with a nuclear umbrella. Rodong in a separate commentary Thursday said the nuclear protection pledge justifies the Norths own nuclear programme. It warned of fiery showers of nuclear retaliation in case of any aggression against it. Officials believe the North will fire short-range or mid-range missiles off its east coast in the next fortnight, after it warned foreign ships to stay clear of a specific area during the period. Washington has also said it is prepared for the Norths possible firing of a long-range missile towards Hawaii, perhaps on or around the July 4 US Independence Day. The North reacted defiantly to a UN Security Council decision on June 12 to impose new sanctions, which tighten a ban on arms shipments among other measures. It vowed on June 13 to build more nuclear bombs from its plutonium resources and to start a separate atomic weapons programme based on enriched uranium. As part of efforts to curb the Norths weapons programmes, a US destroyer is shadowing a suspicious North Korean cargo ship apparently heading for Myanmar. The US Defence Department said the Kang Nam 1 was still being monitored but declined to say where it was, or if or when the US Navy might ask to search it. State media in military-ruled Myanmar said it had no information on the Kang Nam 1. Singapore said the ship has not asked permission to dock there.