Radical preacher Anjem Choudary has had his assets frozen, days before he is due to leave prison.
The 51-year-old, who was jailed for five-and-a-half years for inviting support for the Islamic State group, is expected to be released on Friday.
The BBC understands police have been preparing a list of up to 20 measures to control the east London preacher.
The government's asset freezing team confirmed Choudary had been listed on a global record of known terrorists.
Former Met terror chief Richard Walton told BBC Newsnight that Choudary was a "hardened dangerous terrorist" and someone who has had a "huge influence on Islamist extremism in this country".