Tencent's spokesman Zhang Jun responded on Friday, saying the company is in contact with related Russian agencies.

Currently, some WeChat users in Moscow have been unable to log in or send messages.

MOSCOW, May 5 (Xinhua) -- Russia on Friday banned the access to Chinese instant messaging app WeChat, saying its operator failed to register with the appropriate authorities.

On Tuesday, Roskomnadzor also blocked Messenger, Line and Vchat for the same reason.

China's instant messaging app WeChat is seen on a phone in Moscow, Russia, May 6, 2017. (Xinhua/Shi Hao)

Vadim Ampelonsky, spokesman of Russian telecommunication watchdog Roskomnadzor, said WeChat "did not provide the contact information necessary for registration with authorities."

WeChat is the most popular messenger app in China and is widely used by Chinese living overseas. It is produced by China's IT giant Tencent.