More proof that the Moscow criminal community hasn't been too busy to do its homework: In the space of the last week and a half, two sophisticated art heists have been pulled off in the Arbat area, both involving rare, well-guarded collections.


In the first, occurring Dec.15, an unknown thief or thieves walked into the Russian State Library -- formerly known as the Lenin Library -- and managed to steal in broad daylight a pair of extremely valuable rare books from a display case equipped with an alarm.


In the second incident Monday, a gang of thieves entered the home of an elderly art collector on Novy Arbat and stole 13 valuable paintings, including a portrait by the renowned Russian artist Fyodor Rokotov.


"It was an organized theft in which the owner was bound, gagged and knocked out with the butt of a pistol," said Andrei Kisilov, a spokesman for the Moscow Police.


Kisilov was not at liberty to say which paintings were taken, although he did say that the collection included both Russian and foreign artists, among those the Dutch artist Terens. He also declined to put a value on the stolen items.


The theft at the library resulted in the loss of two of the library's most valuable manuscripts, the "Constitution of Venice," written by Pope Clement V in 1500, and "Proverbs and Sayings," written by Erasmus of Rotterdam in 1508.


According to Vladimir Volpinsky, an assistant director of the library, the auction value of the two books combined is approximately $20,000.


The books were stolen during the day after the alarm system had been somehow deactivated. A janitor noticed the books were missing at the end of the work day. Police spokesmen speculate the theft may have been facilitated by an accomplice on the library staff.


Rare books have become Russia's latest target for thieves since state bookstores began to be deregulated in 1993-1994. Previously, the state was obligated to sell a book at its list price regardless of how old it was, and many collectors made off with thousands of dollars worth of rare books for pennies.


"It was a system in which one could go in to a store, ask to see all the copies of, for instance, Dead Souls , and come out with one that was printed in 1850, or might even have been a first edition," said Valentin Lavrov, an author who also owns one of Moscow's most extensive private book collections. "Now those books are harder to find -- and thieves are beginning to seek them out."