Nazi Germany tested a crude nuclear device in March 1945, killing hundreds of people in a massive explosion south of Berlin, a German researcher claims in a new book published Monday.

That the Nazis conducted nuclear experiments has been known for decades, but "Hitler's Bomb," by Berlin academic Rainer Karlsch (search), suggests they may have been closer to building an atomic weapon for military use than previously believed.

No independent corroboration of the claims was immediately available.

"German physicists did not lag behind their colleagues in the United States and Britain in their understanding of theory," Karlsch told a news conference. "They knew what a plutonium bomb was and what a uranium-235 bomb was."

What Nazi Germany lacked was enough fissile material (search) — such as enriched uranium — to make a full-size, functioning nuclear bomb, he said.

Other researchers already have theorized that the Nazis conducted crude nuclear experiments, but Karlsch said he has discovered additional evidence, notably in the archives of the former Soviet Union.

The book cites postwar witness accounts and Soviet military intelligence reports to back up its theory of a March 3, 1945, experimental nuclear test blast at the Nazis' Ohrdruf military testing area (search), but it offers no direct documentary proof.

Karlsch acknowledged he had no positive proof the Nazis conducted a nuclear test blast, but he hoped his book would provoke more research. Soil samples that Karlsch had analyzed for his book found the presence of radioactive isotopes (search), he said.

Witnesses reported a bright flash of light and a column of smoke over the area that day, and residents said they had nausea and nosebleeds for days afterward, Karlsch says.

One witness said he helped burn heaps of corpses inside the military area the next day. They were hairless and some had blisters and "raw, red flesh."

Karlsch concludes that the blast killed several hundred prisoners of war and Nazi inmates forced to work at the site. Two months later, on May 8, 1945, Nazi Germany surrendered after the Soviets captured Berlin.

Ohrdruf, located in the southeastern state of Thuringia, was a Soviet military base after World War II.