The hacker used Medvedev's page to declare the PM's intention to resign and pursue a career as a freelance photographer, RT News reported.
"I resign. I am ashamed for the actions of the government. I'm sorry," the first tweet said.
"I've been longing to say this. Vova [Putin]! you are wrong!" another tweet said.
Apparently the hacker is Russian, since the messages show good knowledge of Russian politics.
For instance, his/her latest tweet addressed to President Vladimir Putin is a reference to the famous words of Mikhail Gorbachev, who said "Boris, you are wrong!" to Boris Yeltsin in response to his criticism of the Communist Party in 1988.