Twitter has suspended the account used by Somalia's al-Qaeda-linked militant group after the insurgents used the micro blogging site to post a hostage video and death threat.
The al-Shabab-run Twitter account @HSMPress was suspended on Sunday, two days after al-Shabab used the platform to announce a death threat against Kenyan hostages unless Kenya's government meets its demands.
Twitter's terms of service says it does not allow specific threats of violence against others in its posts.
Terrorism analysts say that the militants' use of Twitter has upsides and downsides. Analysts and governments can use militants' Twitter postings to gather intelligence, but militants can use the accounts to spread propaganda or recruit fighters.
Al-Shabab uses Twitter mainly to make claims of enemy kills and to spread its view of events in Somalia and East Africa. Terrorism analysts believe the account is run by a Western-educated person; al-Shabab claims several dozen American and Britons among its ranks.
On January 16 al-Shabab posted a statement saying it planned to kill Denis Allex, a French hostage who was the subject of a botched rescue attempt by France's military. Al-Shabab shortly thereafter used Twitter to announce Allex's death.
French officials say they believe Allex died during the January 11-12 rescue attempt.
"I'm in favour of allowing them to continue (using Twitter), but I don't think it should be unfettered," said JM Berger, a terrorism analyst who runs the website Intelwire.com.
"They clearly crossed the line threatening to kill someone and that person ended up dead. It's in Twitter's interest not
to allow that kind of thing."
Berger sent a public tweet to Twitter shortly after al-Shabab posted its death threat against the Kenyans on Wednesday alerting Twitter to the terms of service violation. He said he suspects al-Shabab is already back on Twitter, and he noted several accounts similar to the @HSMPress account.
Al-Shabab joined Twitter in late 2011 after Kenyan forces moved into southern Somalia. Early tweets by al-Shabab mocked a Twitter posting by Kenya's army spokesman, Maj. Emmanuel Chirchir, that threatened to bomb concentrations of donkeys that might be moving weapons for the insurgents.
The two sides traded several virtual jabs.
Several terrorism analysts, including Berger, have recently engaged another Twitter account in a running conversation.
The experts believe that account is run by Omar Hammami, an American from the state of Alabama who joined al-Shabab about six years ago. Hammami - whose nom de guerre is Abu Mansoor Al-Amriki, or "the American" - has used Twitter and YouTube to publicise a falling out with al-Shabab.
Hammami announced through his Twitter account this month that al-Shabab had threatened to kill him last Saturday if he did not turn himself in. He later said the death threat was revoked and that al-Shabab was afraid of the media fallout of killing an American militant.