UPDATE: 11:40 p.m. EDT — The outage affecting Telegram messenger is over now, even though the reason behind the service going offline for about an hour Tuesday night is still unknown. Users of the service around the world — from Italy, the United Kingdom, China, Kazakhstan, Austria, Brazil, and the Netherlands, among others — posted messages on social media, saying Telegram was working again.

Original story:

Popular messaging service Telegram went offline without warning Tuesday night, leaving many users around the world without a solution to fix it. The outage is affecting not only the secure messenger’s app, but also its website, which only returns a “501 Internal Server Error.”

According to downdetector.com, the outage was first reported at 10:38 p.m. EDT. Based on comments on social media, the problem affected users in countries across the world, including the United States, the United Kingdom, Portugal, India, the Netherlands, China, Ukraine, Finland, Canada, Iran, Turkey, Libya, Kenya, Nigeria, Ecuador, Saudi Arabia, Australia and many others. Some users also tried using VPN (virtual private network) services to get around potential government blockage of the service, but to no avail.

Telegram, developed by Pavel Durov, was banned in his native Russia on Monday morning, when authorities asked mobile service providers to block access to the messaging service. It came at the end of a long tussle between Russian authorities and Durov, with the former wanting access to Telegram users’ data, a request the latter denied. Durov posted a message Tuesday evening about the ban in Russia.

This IBT reporter independently verified that Telegram was accessible in Russia on Monday and Tuesday, with people using VPN in case the service did not work for them the usual way. However, when the service went down — which was early Wednesday morning in Russia — Russian users were affected too.

Durov, who has in the past provided updates about localized outages of Telegram, had not issued any comment on the latest outage at the time of writing.