Twitter has reacted to a series of hacking attacks on high-profile media organisations by beefing up its security.
The social networking site has begun a roll-out of an optional “login verification” service to prevent hackers accessing private accounts.
A number of media groups have seen their Twitter accounts hijacked in recent weeks.
Last week, a group of hackers known as the Syrian Electronic Army infiltrated several Financial Times Twitter accounts along with its own blog where a headline briefly read “Syrian Electronic Army Was Here”.
The SEA has previously claimed responsibility for hacking attacks on Twitter accounts of the BBC, Sky News, the Guardian and Associated Press.
In April, AP tweeted messages claiming there had been explosions in the White House and that President Barack Obama had been injured. An account with links to the SEA claimed it was behind the hoax.
Twitter last month warned news organisations to tighten up security in the wake of the attacks.
The new system will allow users to opt in to a two-step process requiring a verification code for every sign in.
The BBC website quotes Twitter’s product security head Jim O’Leary as saying: “You'll need a confirmed email address and a verified phone number. After a quick test to confirm that your phone can receive messages from Twitter, you're ready to go.”