(Telecompaper) Mobile messaging and VoIP app Viber reached 920 million unique users in June, up from 891 million in March and 823 million in June 2016. According to its parent company Rakuten, Viber's second-quarter revenues were up 91 percent year-on-year, driven by more customers making calls with Viber Out and increased content purchases. Telecom accounted for 73 percent of Viber's revenue and content the remainder.