Many protesters in the city have used Telegram to evade electronic surveillance and coordinate their demonstrations against a controversial Beijing-backed plan that would allow extraditions from the semi-autonomous territory to the mainland.
Demonstrations descended into violence Wednesday as police used tear gas and rubber bullets to disperse protesters who tried to storm the city's parliament -- the worst political crisis Hong Kong has seen since its 1997 handover from Britain to China.
Telegram announced late Wednesday that it was suffering a "powerful" Distributed Denial of Service (DDoS) attack, which involves a hacker overwhelming a target's servers by making a massive number of junk requests.
It warned users in many regions may face connection issues.
Pavel Durov, Telegram's CEO, said the junk requests came mostly from China.
"Historically, all state actor-sized DDoS (200-400 Gb/s of junk) we experienced coincided in time with protests in Hong Kong (coordinated on @telegram)," he tweeted.
"Imagine that an army of lemmings just jumped the queue at McDonald's in front of you -– and each is ordering a whopper," it said, referring to the flagship product of Burger King.
"The server is busy telling the whopper lemmings they came to the wrong place -– but there are so many of them that the server can't even see you to try and take your order."
China's foreign ministry and cyberspace administration did not immediately respond to AFP's requests for comment.
Telegram allows users to exchange encrypted text messages, photos and videos, and also create "channels" for as many as 200,000 people. It also supports encrypted voice calls. It announced last year that it had crossed 200 million monthly active users.
