Authorities have thwarted two attempts to break into Russian military nuclear facilities since the 1991 collapse of the Soviet Union (search), a Defense Ministry official said Wednesday.

There have been no terrorist attacks on the facilities, but civilians twice tried unsuccessfully to gain illegal access, said Col. Gen. Igor Valynkin (search), chief of the ministry's 12th Main Department, which is in charge of atomic weapons.

The attempts to penetrate military nuclear installations occurred in 2002 and 2003, both in the European part of Russia, Valynkin said. In both cases, the attempts involved one intruder.

The attempts "were averted by our mobile units and security at the facilities," he said, asserting they were reliably protected from penetration by intruders and potential terrorist attacks.

"Our system is good; it works and it provides nuclear security," he said.

However, Valynkin acknowledged that "there are problems with nuclear security" and said it is being improved with help from the United States and other foreign donors, including by installing security systems that eliminate the need for human guards.

"The human factor plays a role everywhere," he said. "If you place a guard at an installation, he is doubtless a protector, but he also can be an individual who either violates or aids in the violation or penetration of the facility."

He said Russia is using U.S. and German funding, as well as its own money, "to strengthen our facilities with security systems. This enables us to take away the guard and fully control it through technical means of protection."

Valynkin said the main source of a potential terrorist threat to the Kremlin's nuclear weapons facilities is "Chechen terrorist groups," which have warned that they will target Russian facilities of all kinds.

He suggested there had been warnings from the Federal Security Service, or FSB, indicating potential terrorist threats to specific installations, but he would not discuss the issue in detail.

"We get special information from the FSB on terrorism and their plans as to our facilities, and in connection with this we immediately take measures at these facilities," he said.