Seoul, May 25 (Inditop) North Korea said Monday it “successfully” conducted a nuclear test and also appeared to have fired a short-range missile, following up on earlier threats issued after the UN Security Council criticised a rocket launch by the Stalinist state.

“According to the demand of our scientists and technicians, our republic has successfully conducted another underground nuclear test on May 25… as part of measures to strengthen its nuclear power in self-defence,” the state-run Korean Central News Agency said.

“The current nuclear test was safely conducted on a new higher level in terms of its explosive power and technology of its control and the results of the test helped satisfactorily settle the scientific and technological problems arising in further increasing the power of nuclear weapons and steadily developing nuclear technology,” the statement said, but did not give any details about the test or its location.

A South Korean official, quoted by the Yonhap news agency, said earlier South Korea had detected artificial tremors around 0054 GMT, which were indications of a nuclear test.

“An artificial earthquake was detected at 9:54 a.m. this (Monday) morning near Poongkye-ri in North Hamkyong Province,” Lee Dong-kwan, a spokesman for the South Korean president’s office, was quoted as saying by the Yonhap news agency.

Seoul’s weather agency said the test was conducted about 10 to 15 km from the location of Pyongyang’s first nuclear test in October 2006, which met with widespread condemnation from the international community.

The quake’s magnitude was 4.5 on the Richter scale, the defence ministry said. The US Geological Survey also confirmed the quake’s location 380 km north-east of Pyongyang and approximate magnitude at 4.7.

In addition to the nuclear test, the communist state apparently also test-fired a short-range ballistic missile with a range of 130 km on its east coast, Yonhap reported, quoting a South Korean source.

The US State Department in Washington remained cautious, telling DPA that it was looking into the reports.

“We are gravely concerned by North Korea’s claims,” a US State Department official said. “We are analysing the data. The US Geological Survey confirmed that a seismic event took place consistent with a test. We are consulting with our six-party and UN Security Council partners on next steps,” the official said, referring to international talks aimed at halting North Korea’s nuclear weapons programme.

The Security Council censored North Korea’s April 5 rocket launch, which was widely regarded as a cover for a ballistic missile test.

South Korean President Lee Myung Bak ordered an emergency meeting of the country’s National Security Council. The country put its troops on heightened alert.

In reaction to the test, Japan said it planned to request an emergency meeting of the UN Security Council.

“If the nuclear test is confirmed, it is a clear violation of UN Security Council resolution and Japan will take decisive measures,” Chief Cabinet Secretary Takeo Kawamura said.