Moscow: Vladimir Putin was sworn in as Russia's president for a fourth term on Monday, extending his almost two-decade rule by another six years at a time of high tension with his Western rivals.
The 65-year-old, in power since 1999, is on course to become the longest-serving Russian leader since Joseph Stalin after his victory in March's elections.
Putin won nearly 77 percent of the vote in polls which his most vocal opponent was banned from running in.
He has promised to use his fourth term to revitalise the country's economy. But he also faces a host of delicate international disputes.
"I consider it my duty and my life's aim to do everything possible for Russia, for its present and for its future," Putin said at Monday's swearing-in ceremony, with his hand on the Russian constitution.
Elite guests lining the red carpet filmed Putin on their smartphones as he arrived for the swearing-in ceremony in the ornate Andreyev Hall, part of the Kremlin palace complex.
The car that brought him to the inauguration was a black Russian-made limousine -- a change from previous ceremonies when he used a Mercedes.
"I feel strongly conscious of my colossal responsibility," he said, thanking Russians for their "sincere support" and "cohesiveness." "We have revived pride in our fatherland," Putin said.
"As head of state I will do all I can to multiply the strength, prosperity and fame of Russia."
Opposition leader Alexei Navalny called on Russians to protest across the country on Saturday under the slogan "Not our Tsar".
On Saturday nearly 1,600 protesters including Navalny were detained during nationwide rallies against Putin.
The European Union condemned what it called "police brutality and mass arrests" during the protests.
Police in Moscow were helped by pro-Putin activists dressed as Cossacks, a paramilitary class who served as tsarist cavalrymen in imperial Russia.
The unrest revived memories of 2012, when authorities cracked down on rallies against Putin's return to the Kremlin from the post of prime minister.
Navalny was barred from challenging Putin in the March election over a fraud conviction that his supporters say is politically motivated.
Russia's ties with the West have been strained by Putin's moves to annex Crimea from Ukraine and to launch a military campaign in Syria in support of its President Bashar al-Assad.
In recent months relations have soured further over accusations of the poisoning of an ex-spy in Britain and of election meddling in the US.
"For Putin any concession is a sign of weakness, so there shouldn't be any expectation of a change in foreign policy," said Konstantin Kalachev, the head of the Political Expert Group think tank in Moscow.
But independent political analyst Dmitry Oreshkin said the president may find himself obliged to shift his approach to the international community over the next term.
"Russia hasn't been so isolated since the Soviet war in Afghanistan" from 1979 to 1989, he told AFP.
"Now his task isn't to bring any new lands to Russia, but to force the world to consider Russia's interests and accept its previous conquests." Reports that Alexei Kudrin - a liberal former finance minister who is respected abroad - could return to the Kremlin in a reshuffle, suggest the president could be seeking a less confrontational approach.
The constitution bars Putin from running again when his fourth term ends in 2024. But he has remained silent on the issue of his succession.
Oreshkin said Putin would stay on for the full term but Kalachev suggested he could leave the Kremlin before he serves out the six years.
"He will stay in power, but not necessarily in the presidency," he said. "For Putin to write his place in history, he needs to pick the right moment to go. Serving another six years is a road to nowhere. He will leave in a way that takes everyone by surprise."
Putin has promised to use his fourth term to improve Russian living standards.
"People will live better," he said.
"We need breakthroughs in all spheres of life. I am deeply convinced that such a breakthrough can only be achieved by a free society that accepts everything new and progressive, and rejects injustice." Russian businesses are expecting wide-ranging reforms.
Putin has struggled to revive an economy that crashed after Moscow was hit with Western sanctions over Crimea and by a fall in global oil prices.