South Korea has detected levels of radiation eight times higher than normal along its border with North Korea, according to reports. North Korea last month said it conducted a nuclear fusion test—a step toward building a hydrogen bomb.

South Korea quickly disputed the North's claim of a successful nuclear fusion test on May 12. But two days after the alleged test, high levels of radioactive xenon gas were detected on the border between the two Koreas. The last time North Korea tested a nuclear weapon, in 2006, high levels of xenon were detected in the air. A nuclear expert told South Korean newspaper The Chosun Ilbo that "an atomic bomb is used to compress the tritium in hydrogen bombs. If xenon was detected, it must have been produced in such a process."

Less than two weeks ago, North Korea became fed up with the South for blaring K-Pop from loudspeakers placed along the 38th Parallel, and threatened to turn the capital Seoul "into a sea of flame" if they didn't turn the music down. The South has accused North Korea of sinking its warship Cheonan in March, and has been playing bad music along the border in retaliation.

[Image via AP]