Moscow ? A Russian archaeologist says he has found the lost capital of the Khazars, a powerful nation that adopted Judaism as its official religion more than 1,000 years ago, only to disappear leaving little trace of its culture.

Dmitry Vasilyev, a professor at Astrakhan State University, said his nine-year excavation near the Caspian Sea has finally unearthed the foundations of a triangular fortress of flamed brick, along with modest yurt-shaped dwellings, and he believes these are part of what was once Itil, the Khazar capital.

By law Khazars could use flamed bricks only in the capital, Vasilyev said. The general location of the city on the Silk Road was confirmed in medieval chronicles by Arab, Jewish and European authors.

Kevin Brook, the American author of “The Jews of Khazaria,” e-mailed Wednesday that he has followed the Itil dig over the years, and even though it has yielded no Jewish artifacts, “Now I’m as confident as the archaeological team is that they’ve truly found the long-lost city,

The Khazars were a Turkic tribe that roamed the steppes from Northern China to the Black Sea. Between the 7th and 10th centuries they conquered huge swaths of what is now southern Russia and Ukraine, the Caucasus Mountains and Central Asia as far as the Aral Sea.

Itil, about 800 miles south of Moscow, had a population of up to 60,000 and occupied 0.8 square miles of marshy plains southwest of the Russian Caspian Sea port of Astrakhan, Vasilyev said.

It lay at a major junction of the Silk Road, the trade route between Europe and China, which “helped Khazars amass giant profits,” he said.

The Khazar empire was once a regional superpower, and Vasilyev said his team has found “luxurious collections” of well-preserved ceramics that help identify cultural ties of the Khazar state with Europe, the Byzantine Empire and even Northern Africa.

But a scholar in Israel, while calling the excavations interesting, said the challenge was to find Khazar inscriptions.

“If they found a few buildings, or remains of buildings, that’s interesting but does not make a big difference,” said Dr. Simon Kraiz, an expert on Eastern European Jewry at Haifa University. “If they found Khazar writings, that would be very important.”

Vasilyev says no Jewish artifacts have been found at the site.