President Vladimir Putin has been sworn in for a new six-year term at a ceremony that was boycotted by the United States and a number of other Western countries because of Russia’s war in Ukraine.

Putin, in power as president or prime minister since 1999, begins his new mandate more than two years after he sent tens of thousands of troops into Ukraine, where Russian forces have regained the initiative after a series of reversals and are seeking to advance further in the east.

During Tuesday’s inauguration in the Grand Kremlin Palace for a record fifth presidential term, Putin said Russia would pass through the current “difficult” period stronger and emerge victorious.

“We are a united and great nation, and together we will overcome all obstacles, realise everything we have planned, and together, we will win,” he said.

At 71, Putin dominates the domestic political landscape. On the international stage, he is locked in a confrontation with Western countries he accuses of using Ukraine as a vehicle to try to defeat and dismember Russia.

In March, Putin won a landslide victory in a tightly controlled election from which two antiwar candidates were barred on technical grounds.

His best-known opponent, Alexey Navalny, died suddenly in an Arctic penal colony, and other leading critics were either jailed or forced to flee abroad.

Navalny’s widow, Yulia Navalnaya, on Tuesday urged supporters to keep up the fight against Putin, who she described as “a liar, a thief and a murderer”.

Ukraine said the inauguration sought to create “the illusion of legality for the nearly lifelong stay in power of a person who has turned the Russian Federation into an aggressor state and the ruling regime into a dictatorship”.