Russia's new President, Dmitry Medvedev, says his priorities in government will be to safeguard civil and economic freedoms.
Mr Medvedev was speaking after he was sworn in as Russia's third president since the fall of the Soviet Union in 1991.
The 42-year-old former corporate lawyer and long-time Putin ally took the oath of office and received a gold chain of double-headed eagles symbolising the presidency at a ceremony at the Kremlin.
He inherits a booming economy fuelled by high oil prices, but also a sobering set of challenges. These include rampant corruption, rising inflation, a falling population, sickly industry and increasingly tense relations with former Soviet neighbours and the West.
Vladimir Putin, who stepped down after serving two terms in the position, is to be his Prime Minister.
Over 2,000 invited dignitaries attended the ceremony at the Kremlin which stressed continuity and a smooth transition of power.
Mr Putin named 42-year-old Mr Medvedev as his preferred successor, ensuring his victory in presidential elections last March with 72% of the vote.
Mr Putin has also said he will retain political influence but has pledged not to change the balance of power between president and government.
'As I hand over the powers of the head of state, I would also like to say that the responsibility of protecting Russia was and remains my civic duty. I have kept to it all these years and will keep to it my whole life,' he added.
Mr Putin was prevented from seeking office again by a constitutional ban on more than two consecutive terms in office, but it is thought he may try to regain the presidency after Mr Medvedev leaves.
Eight years ago, the departing Boris Yeltsin left Mr Putin a pen with which he used to sign laws as a symbol of a handover of power. Mr Putin said in a newspaper interview last month that he would take the historic pen with him rather than leave it to Dmitry Medvedev.
