A denial-of-service attack took down a website that had been started by organizers of the upcoming opposition rally "Big White Circle," which aims to form a human circle around downtown Moscow.

The site first went down Monday, and as of Tuesday morning it was back online but with limited functionality.

Organizers posted a note on their Facebook page about the attack, which also affected other clients that use the same server as the rally website.

The site, Feb26.ru, displays a map of downtown Moscow and is designed to inform people of places along the Garden Ring — the site of the demonstration — that require more participants to close the circle. The rally is set for Sunday afternoon.

Organizers estimate that a minimum of 34,000 participants are needed to complete the circle. As of Tuesday, the site showed more than 6,300 participants signed up for the rally.

The opposition group began searching for another host for the site, saying the company currently hosting it could not give an estimate about when it would come back online.

"Because there is reason to believe that in Russia this site will not survive, we are looking for an option that federal investigators call a 'foreign server.' There are options," the group We Were at Bolotnaya and Will Go Again said on Facebook.

Organizers said they were unsure how long a move of the site would take, but said they had managed to save almost all the information on the site.