Police violently broke up unsanctioned rallies, including in Saint Petersburg where more than 450 people were detained.
In a statement, Google-owned YouTube said it considered all all valid requests from governmental bodies, adding: "We require advertisers to comply with local law and our general advertising policies".
"I have come here to protest against the pension reform, I have to live in this country and I want to have hope for the future and a good old age", said 22-year-old Nikolai Borodin.
Putin's trust rating in public opinion polls dropped notably after the proposal was put forward and last month offered some concessions, including dropping the age for women from 63 to 60.
Thousands of Russians in more than 80 cities and towns protested proposed government pension reforms on Sunday.
Thousand of Russians arrested at mass riots against retirement-age increase
The proposed pension changes, which are now going through parliament, have shaved around 15 percentage points off President Vladimir Putin's popularity rating.
A demonstration in Moscow's Pushkin Square attracted around 2,000 people, who chanted slogans such as "Russia without Putin" and held signs reading, "Putin, when will you go on pension?" The city of Yekaterinburg in the Urals saw the highest number of arrests - 58 in total, the group said.
Russian President Vladimir Putin's close ally has been overwhelmingly re-elected Moscow's mayor, election officials said on Monday, following a poll overshadowed by protests over a pension reform. Social media showed footage of police hitting protestors with batons in Moscow as their colleagues tried to wrench them out of the police's grip. After the bill on the pension reform was submitted to Russia's parliament in June, Putin's approval rating fell from a peak of 74 percent in 2015 to 45 percent on August 5 - the lowest point since 2013, according to Russia's FOM polling agency.
There were other protests in cities across Russian Federation.
United Russia also suffered defeats to the Communists in party-list votes for three regional parliaments.
He said the protests had nothing to do with the elections and highlighted that Google took down the ads in various regions, even if they didn't have elections scheduled for Sunday. Average life expectancy for men in Russian Federation is 66 and for women 77. However, analysts say it's unlikely that they will have an impact on results, as opposition candidates have been barred from standing.