The announcement of the suspension came in the form of a brief statement to those accessing the group's handle, The New York Times reported Friday.
"Account suspended," the message at @HSMPRESS1 said. "The profile you are trying to view has been suspended."
Twitter does not comment on individual suspensions, the Times said.
Al-Shabaab released a statement saying Twitter is engaged in "another futile attempt to silence the truth and the factual coverage of events in Somalia."
Al-Shabaab has been on Twitter since 2011. The account had about 6,000 followers, many of them journalists.
The group's account was suspended in January when threats to kill hostages were posted.
The initials HSM stand for Harakat al-Shabaab al-Mujahedeen or Mujahedeen Youth Movement, al-Shabaab's official name.
The group's tweets are sent in English, suggesting they are aimed at a global audience, including the news media. They show familiarity with the language, with the person creating them possibly a native English-speaker or someone who has lived outside of Somalia for a long time, the Times said.