"I resign. I am ashamed of the government's actions. I'm sorry," the tweets began, in Russian.
The Russian hacking collective Shaltay Boltay, whose name means Humpty Dumpty, took credit for the takeover, tweeting out denunciations of President Vladimir Putin and the country's takeover of Crimea.
On its own account, the Anonymous-affiliated group tweeted: "Several mail accounts -- including the Gmail and the content of three iPhones of a certain prime minister have randomly fallen into our hands on the Internet. Details later."
Shaltay Boltay last month published what it said were notes from the Kremlin instructing Russian television stations on how to cover major news events, private messages of a pro-Kremlin group charged with making pro-Putin comments on Western news sites, and leaked emails from the Russian rebel commander in eastern Ukraine, Igor Girkin, going back as far as 2010.
Несколько почтовых акков в том числе гмайл и содержимое трех айфонов некоего премьер-министра случайно попалось нам в сети Подробности позже— Shaltay Boltay (@b0ltai) August 14, 2014
Below are some of the tweets from Medvedev's hacked account, with translations:
Photos Shaltay Boltay claimed were taken from Medvedev's phone, which appear to be from a government meeting, from Medvedev's normal vantage point.