"Several mail accounts, including Gmail and the contents of three iPhones belonging to a certain prime minister, have been sent to us completely coincidentally," he wrote, providing a link to Shaltay Boltay's official Twitter account, @b0ltai.
Leviyev also posted a picture of what appeared to be participants engaged in a meeting, saying he believed it had been downloaded from Medvedev's phone. More details would be provided later, he said in a separate message. The hacking, which took place Thursday morning, saw a series of satirical tweets posted from the official Twitter account of Medvedev, including one saying he was going to resign.
"I'm going to become a freelance photographer!" one tweet said.
The prime minister's press service was quick to deny the tweets' authenticity, telling the Interfax news agency that the account had been compromised and that the incident was being investigated. Despite denying any official involvement in the hacking, Shaltay Boltay has a reputation for gaining clandestine access to the accounts of Russian politicians and publishing their private correspondences online.
Most recently, in July, the group hacked into Deputy Prime Minister Arkady Dvorkovich's private e-mail account and uploaded a number of his letters and reports to its blog. In response, the government's media watchdog asked Internet operators to block access to the group's website, the ITAR-Tass news agency cited a spokesman for the regulator as saying.