Russian social networking site Odnoklassniki will begin charging for registration, Lenta.ru reported Friday.

After completing registration information, users are asked to send an SMS in order to actively participate in the social network's features like sending messages, commenting on photos and on other users' profiles as well as visiting members' pages.

The site's creators said the activation procedure will only be required once. The step is a necessary measure to keep Odnaklassniki in order and to prevent members from automatically receiving spam, Lenta.ru reported.

The social network already earns money through banner ads. Members can also pay a fee to upload additional photos. In addition, it recently launched a paid option for users to be able to hide when they are online.

The cost for an SMS ranges from RUB29 (US$1.1) to RUB35 ($1.3). Users who are already registered will not be obliged to go through this procedure.

Odnaklassniki is the largest social network in Russia and has around 22 million users.