North Korea has restarted its weapons-grade nuclear power plant and fired off its sixth short-range missile, news reports said Wednesday, deepening a standoff with world powers following its latest nuclear test.
Meanwhile, North Korea's military says it considers South Korea's participation in a US-led program to intercept ships suspected of spreading weapons of mass destruction tantamount to a declaration of war against the North.
The communist North's military said in a statement Wednesday that it will respond with "immediate, strong military measures" if the South actually stops and searches any North Korean ships under the Proliferation Security Initiative.
The statement, carried by the North's Korean Central News Agency, said North Korea no longer considers itself bound by the armistice that ended the Korean War, as a protest over the South's participation.
South Korea announced its participation in the anti-proliferation program Tuesday, one day after the North conducted a nuclear test.
The missile launches over the past two days came as the UN Security Council debated possible new sanctions against the isolated communist nation for its nuclear test on Monday. Retaliatory options were limited, however, and no one was talking publicly about military action.
South Korea's mass-circulation Chosun Ilbo newspaper reported that US spy satellites have detected steam coming from a nuclear facility at North Korea's main Yongbyon plant, indicating the North is reprocessing spent nuclear fuel rods to harvest weapons-grade plutonium.
Its report quoted an unnamed official. South Korea's Defense Ministry and the National Intelligence Service – the country's main spy agency – said they cannot confirm the report.
The North had said it would begin reprocessing in protest over international criticism of its April 5 rocket launch.
North Korea is believed to have enough plutonium for at least half a dozen atomic bombs. The North also has about 8,000 spent fuel rods which, if reprocessed, could allow the country to harvest 6-8 kilograms (13-18 pounds) of plutonium _ enough to make at least one nuclear bomb, experts said.
North Korea test-fired three short-range missiles Tuesday, including one late at night, from the east coast city of Hamhung, according to South Korea's Yonhap news agency. South Korea's spy chief confirmed two other missiles were launched Monday, but reports put the number at three Monday for a total of six.
More could be planned.
North Korea has warned ships to stay away from waters off its west coast through Wednesday, suggesting more test flights.
Details of Monday's nuclear test may take days to confirm. Russian defense officials said the blast was roughly as strong as the bombs dropped on the Japanese cities of Hiroshima and Nagasaki in World War II and was stronger than North Korea's first test in 2006.
In New York, UN diplomats said key nations were discussing a Security Council resolution that could include new sanctions against North Korea.
Ambassadors from the five permanent veto-wielding council members – the United States, Russia, China, Britain and France – as well as Japan and South Korea were expected to meet again soon, the diplomats said, speaking on condition of anonymity because the meeting is private.
The Security Council met in emergency session Monday and condemned the nuclear test. Council members said they would follow up with a new legally binding resolution.
How far China and Russia, both close allies of North Korea, would go remained the main question.
Russia, once a key backer of North Korea, condemned the test. Moscow's UN ambassador, Vitaly Churkin, also the Security Council president, said the 15-member body would begin work "quickly" on a new resolution.
Chinese Foreign Ministry spokesman Ma Zhaoxu also said Beijing "resolutely opposed" the nuclear test. It urged Pyongyang to return to negotiations under which it had agreed to dismantle its atomic program.
North Korea is "trying to test whether they can intimidate the international community" with its nuclear and missile activity, said Susan Rice, US ambassador to the United Nations.
"But we are united, North Korea is isolated, and pressure on North Korea will increase," Rice said.
Diplomats acknowledged, however, that there were limits to the international response and that past sanctions have had only spotty results.
North Korea seemed unfazed by the condemnation.
Thousands of Pyongyang residents, including senior military and party officials, gathered Tuesday in a stadium to celebrate the successful nuclear test.
Choe Thae Bok, a high-ranking party official, was quoted by North Korea's official news agency as saying that the nuclear test "was a grand undertaking" to protect the country against "the US imperialists' unabated threat to mount a preemptive nuclear attack and (put) sanctions and pressure upon it."
North Korea blamed the escalating tensions in the region on Washington, saying the US was building up its forces, and defended its nuclear test as a matter of self-preservation.
At the Conference on Disarmament in Geneva, An Myong Han, a diplomat from the North Korean mission, said his country "could not but take additional self-defense measures, including nuclear tests and the test launch of long-range missiles, in order to safeguard our national interest."