SAN FRANCISCO - Twitter has, for the first time, sent warnings to a number of users that their accounts may have been hacked by "state-sponsored actors", according to reports.
The hackers may have sought their e-mail or IP addresses, or phone numbers, which it recently began collecting, according to the e-mail Twitter sent to affected users.
The number of accounts affected by the suspected hack is unclear, reported BBC News.
Some of the users who tweeted about receiving the notice on Friday were cryptographers, security researchers, activists or journalists. Twitter confirmed that it had sent the e-mail about state-sponsored actors, but declined to comment further, according to the Financial Times.
Coldhak, a Canadian non-profit organisation, said it had received a warning from Twitter.
"We believe that these actors (possibly associated with a government) may have been trying to obtain information such as e-mail addresses, IP addresses, and/or phone numbers," the e-mail stated.
"At this time, we have no evidence they obtained your account information, but we're actively investigating this matter. We wish we had more we could share, but we don't have any additional information we can provide at this time."
The alert highlights growing concern over hacking activity backed by foreign governments.
For instance, a massive hack last year crippled Sony Entertainment and revealed the inner workings of the studio. US officials blamed the attack on hackers working for the North Korea government.
Other companies such as Google and Facebook already have warning systems to alert users who may be targeted by state-sponsored hackers.