Vladimir Putin was officially sworn in as Russia’s president Monday evening, but protests against his re-election to a third stint in office didn’t end there. Despite hundreds of arrests, protesters stayed out on the streets all day and all night.
Putin, who for the past four years has served as prime minister, replaced Dmitry Medvedev, and once again switched places with him – one of his very first moves as president was to nominate Medvedev as the country’s new prime minister. Russia's parliament confirmed Medvedev's nomination on Tuesday with a 299-144 vote.
Protesters angry at Putin’s return to office for another six years – after 12 years in power, either as president or prime minister – took to the streets of Moscow en masse on the eve of his inauguration Sunday, and again on Monday. Putin’s car, followed by his police motorcycles, drove through empty streets to his inauguration ceremony, out of sight of the police’s clampdown on at least 1,000 protesters. According to official figures, 327 people were arrested Monday; the opposition puts this number closer to 500.
This video compiles footage of multiple protesters being arrested at Moscow's Kitay-Gorod plaza on Monday.

“The police cracked down on protesters much more strongly during Putin’s inauguration than before his election”

Anastasia Kirilenko is a journalist working in Moscow. She spent all Monday and into the early morning hours of Tuesday following the protesters.
Monday’s protests were unauthorized, but the police were ready for them. They wouldn’t let anyone get within 50 metres of the streets the president’s motorcade would drive through. The direction protesters marched kept changing every time the police blocked their way. They chanted, “Put Putin in a gulag!”, “Putin, get out!” and even just “Shame!”
Protesters yell "Shame!" as an elderly protester is arrested.
Protesters ended up gathering at Kitay-Gorod plaza, in front of the presidential administration office, and hundreds of them decided to camp out there overnight. This surprised everyone – it wasn’t planned. Despite frequent arrests, people were in high spirits; some had their guitars out and sang Beatles songs.
Opposition leader Alexey Navalny calls for the protest to continue overnight. He asks those gathered, "Are you serious about staying here?" They yell, "Yes!" He continues: "Ok, then call your friends, and write on Twitter and Facebook that we are organising a sit-in. If you want to leave, wait until someone, or better two people, replaces you here. No tents - they arrest for tents. No alcohol, unfortunately."
The police was less violent than on Sunday – they used street-cleaning vehicles to spray people with water, rather than hit them with their batons.
The police try to disperse protesters with a street-cleaning vehicle. One protester tries to get in the way and is arrested. 
Still, they arrested many protesters; they kept arresting dozens of people at a time throughout the day and into the night. Some of the opposition leaders were even arrested multiple times. But they just kept coming back.
Overall, however, the police cracked down on protesters much more strongly during this inauguration than on the protests before his election. They were more violent with journalists, too. I have a bruise to prove it. And I saw them strike at several journalists’ cameras.
I was impressed to see that the protesters were still at the plaza this morning; they are certainly determined.