The websites of a number of independent media outlets reported coming under apparent hacker attack on Sunday, as thousands gathered in downtown Moscow for an anti-Putin protest.

“Our programmers have confirmed this is a DDoS attack and are trying to get the website back up,” the online TV channel Dozhd said in a Twitter.

Other websites affected were the Moscow-based Ekho-Moskvy radio station, the newswire slon.ru and the Kommersant newspaper.

Opposition media also reported hacker attacks during previous large-scale protest rallies this winter and spring.

Sunday’s rally comes on the eve of the inauguration of Vladimir Putin as Russian president. Putin won a landslide victory in March elections marred by allegations of vote fraud to secure a third term in the Kremlin after being forced to step down by the Constitution in 2008.

Some 8,000 people are currently gathered in downtown Moscow ahead of the rally, police said. Eyewitness at the scene, including a RIA Novosti correspondent gave the figure as around twice that.

Some 3,000 people have also pledged on social network sites to hold an illegal march toward the Kremlin later this evening.