Pavel Durov, founder of the Telegram messaging app, agreed on Wednesday for his firm to be registered in Russia after coming under pressure from the authorities to do so, but said it would not share confidential user data with anyone.
Russia's communications regulator Roskomnadzor had threatened to block the messaging app if it did not hand over information needed to put the app on an official government list of information distributors.
Telegram had refused to comply because it feared that it would undermine the privacy of its more than 6 million Russian users.
Russia's Federal Service for Supervision Of Communications, Information Technology, and Mass Media said on Wednesday that Telegram had now presented all the required data.
"Thereby Telegram started working in the legal framework of the Russian Federation," the Russian watchdog said.
Durov said later via social media that while he was happy for Telegram to be formally registered in Russia and to supply basic information about the company, he would not do anything to violate the app users' privacy.
"We won't comply with ... laws that are incompatible with Telegram's confidentiality policy or protecting people's private lives," Durov said.
After threatening to block Telegram, Russian authorities increased pressure on the company on Monday, saying that terrorists had used the Telegram app to carry out a deadly suicide bombing on Russian soil.
That suggested the authorities were serious about blocking Telegram on national security grounds unless it met their demands.
Durov responded that the app had blocked thousands of terrorism-related channels and that if Russia banned it, terrorists would just switch to a competing service.