Newly inaugurated President Dmitry Medvedev on Wednesday formally assumed control of Russia's nuclear arsenal at a Kremlin meeting in which a military officer brought him a black nuclear briefcase.

Medvedev, who was sworn in to succeed Vladimir Putin earlier, took command in the presence of Defence Minister Anatoly Serdyukov at a sombre meeting that contrasted with his glittering inauguration ceremony.

"Comrade commander-in-chief! Allow me to give you control of the strategic forces of the country," said the officer carrying the nuclear briefcase, in images shown on state television.

The nuclear briefcase, a symbol of political power in Russia since the Cold War, is shrouded in secrecy but believed to contain a small computer with activation codes for nuclear missiles.

Russia's first post-Soviet president, Boris Yeltsin, reportedly came close to using the briefcase in January 1995 when a research rocket launched from Norway activated Russia's early warning system.

The briefcase was developed during the Cold War when it became clear that early warning of a nuclear attack would only give Soviet leaders a few minutes to retaliate -- too little time to travel to a central command centre.

Russia is currently estimated to have around 20,000 nuclear weapons.