MOSCOW - Vladimir Putin took the oath as Russia's president on Monday with a ringing appeal for unity at the start of a six-year term in which he faces growing dissent, economic problems and bitter political rivalries.
Outside the Kremlin's high red walls, riot police prevented protests by rounding up 120 people, including men and women in cafes wearing the white ribbons symbolising opposition to Putin, a day after detaining more than 400 people during clashes.
But in the Kremlin, 2,000 dignitaries applauded Putin's every step down the red carpet into a vast hall with gilded columns, the throne room of tsars, where he was sworn in with his right hand resting on the red-bound Russian constitution.
"We will achieve our goals if we are a single, united people, if we hold our fatherland dear, strengthen Russian democracy, constitutional rights and freedoms," Putin said in a five-minute speech after taking the oath for the third time.
"I will do all I can to justify the faith of millions of our citizens. I consider it to be the meaning of my whole life and my obligation to serve my fatherland and our people."
The Kremlin's bells chimed, and the national anthem bellowed out at the end of a ceremony which was followed by the head of the Russian Orthodox Church blessing Putin and the president taking charge of the nuclear suitcase.
Although he has remained Russia's dominant leader for the past four years as prime minister, Putin, 59, has now taken back the formal reins of power he ceded to his ally Dmitry Medvedev in 2008 after eight years as president.
Parliament is expected to approve Medvedev, 46, as prime minister on Tuesday, completing a job swap that has left many Russians feeling disenfranchised two decades after the Soviet Union collapsed.
Putin is returning with his authority weakened by months of protests that have polarised Russia and left the former KGB spy facing a battle to reassert himself or risk being sidelined by the business and political elites whose backing is vital.
"We want to, and we will, live in a democratic country," Putin declared, evoking patriotic images of Russia as a great nation and urging people to show a sense of responsibility and national pride to make the country stronger.
He made no mention of the protest movement or any policy declarations in his speech.
Despite his pledge, riot police, nervous after battling protesters at an anti-Putin rally on Sunday, cracked down on the slightest sign of dissent on the streets of central Moscow, many of which were left almost entirely empty.
At least 22 protesters were led away when a crowd of more than 100 started shouting "Russia without Putin" near two luxury hotels 500 metres (yards) from the Kremlin.
"This shows that Putin is scared of dissatisfied citizens. Although there are not so many of us, there are not so few either," said 18-year-old student Pavel Kopilkov.
Dozens of others were detained by police on a boulevard near the route of Putin's motorcade to the ceremony, including some who had been sitting outside a French bistro wearing the white ribbon of protest on their jackets and coats.
A Reuters correspondent saw tables and chairs being overturned as the people were hauled away.
"This is shameful. This is not how you celebrate a holiday - this is how you celebrate seizing power," liberal opposition leader Boris Nemtsov said shortly after he was detained.
Moscow police said a total of 120 had been detained for staging unsanctioned pickets and most would soon be released. In Putin's hometown of St Petersburg, police detained a few people in a crowd of dozens at a protest on the central Palace Square.