May 25 (Bloomberg) -- The nuclear device North Korea detonated today was about as powerful as the bomb the U.S. dropped on Hiroshima at the end of World War II, according to Russian estimates.

The North Korean explosion had an explosive yield of between 10 kilotons and 20 kilotons, said Alexander Drobyshevsky, a spokesman for the Defense Ministry, on state television. The blast occurred about 80 kilometers (50 miles) from the northern city of Kilchu, near the borders with China and Russia, Drobyshevsky said.

The “Little Boy” bomb the U.S. dropped on Hiroshima in 1945 had a yield of 15 kilotons, according to the U.S. Federation of American Scientists. The “Fat Man” bomb dropped on Nagasaki had a yield of 21-23 kilotons, according to the research group. A kiloton is an explosive force equal to 1,000 metric tons of TNT.

To contact the reporter on this story: Torrey Clark in Moscow at tclark8@bloomberg.net

Last Updated: May 25, 2009 03:24 EDT