DUBAI (Reuters) - Telegram has raised over $1 billion through bond sales to multiple investors, the messaging app’s founder Pavel Durov said on Tuesday. The funding round included a combined $150 million investment by Mubadala Investment Co and Abu Dhabi Catalyst Partners, which is part-owned by the Abu Dhabi state fund. Although the company did not provide any details about its other investors, Durov said they included “some of the largest and most knowledgeable investors from all over the world.” The funds would be used to help roll out expansion plans as well as drive its monetization strategy, which includes premium plans for business users, Durov said. “Telegram’s user base has reached a critical mass that places it amongst global tech giants,” Mubadala executive Faris Sohail Faris al-Mazrui said in a statement. Telegram, along with messaging app Signal, have seen an increase in users this year amid privacy concerns with larger rival Facebook-owned WhatsApp. It currently has 500 million monthly active users. Telegram, already headquartered in the United Arab Emirates, will open a new office in Abu Dhabi following the new investment, Mubadala said.