First Chinese Nuclear Test in 3 Years Detected

China on Friday carried out its first nuclear test since December, 1984, Swedish military scientists said.

Nils Olof Bergkvist, a spokesman for the Swedish Defense Ministry’s Hagfors observatory, said seismic measurements indicated a “strong explosion in hard rock” at the Lop Nor underground test site in northwestern China close to the Soviet border.

There was no comment from the Chinese government on the reported test.

Bergkvist estimated that the bomb was at least six times as powerful as the one dropped on Hiroshima, which was about 20 kilotons (equivalent to 20,000 tons of TNT). He said it probably was within the 150-kiloton limit agreed to in the unratified 1974 threshold ban treaty between the Soviet Union and the United States.

China maintains a relatively small nuclear arsenal, estimated to contain between 300 and 400 warheads, according to the influential Stockholm International Peace Research Institute.