Yaroslav Nikitenko, an active member of the movement, told RFE/RL that the site, ecmo.ru, was attacked late on the afternoon of August 31. He said the cyberattack might be connected with material about Moscow Oblast Governor Boris Gromov. The attack happened immediately after that material was posted.
The environmental activists plan to ask the Moscow city prosecutor to launch an investigation.
The Khimki Forest Defenders have been campaigning for some time to halt the destruction of thick forest near the Moscow Oblast town of Khimki in order to build a new highway between Moscow and St. Petersburg.
President Dmitry Medvedev last week ordered the construction suspended. Gromov has written to Medvedev and to Prime Minister Vladimir Putin asking them to reconsider that decision.