KIEV, Ukraine — In Russia, likes, reposts, and retweets aren't just endorsements — they're now punishable by up to five years in prison.

President Vladimir Putin has approved new amendments introducing harsh sentences for online incitement to religious hatred and "extremism," further tightening the screws in the Kremlin's recent internet clampdown.

Under the amendments, passed by parliament earlier this month and published on an official government website with Putin's stamp on Monday, prosecutors essentially have the right to charge anyone who reposts content they deem illegal. Russia's vaguely worded "extremism" law is ostensibly aimed at targeting neo-Nazis and Islamic militants, but has been applied to everything from opposition groups to Scientology and South Park, in what rights groups say amounts to backdoor censorship.

The new measures post facto legalize practices Russian authorities have been increasingly keen to avail themselves of during the Kremlin's recent crackdown on the internet, which Putin called a "CIA project" in April. Several cases dating back to last year already indicate actions as trivial as a Facebook like or a retweet could land internet users in jail.

An opposition activist in the remote Siberian city of Barnaul is standing trial for reposting a picture of two bullets with the caption "The only argument the authorities'll hear." In January, police briefly detained a philosophy professor at Moscow State University after he reposted an article theorizing overthrowing the government. A blogger in another Siberian city was arrested last year for retweeting a picture of a leaflet that called on people to trash officials' cars.