In a parliamentary speech Wednesday, Home Secretary Charles Clarke said that in going beyond the boundaries of usual national security measures, the government would have to "tread carefully" around free speech.
Clarke said: "I have decided that it is right to broaden the use of these powers to deal with those who foment terrorism, or seek to provoke others to commit terrorist acts. To that end, I intend to draw up a list of unacceptable behaviours that fall within those powers -- for example, preaching, running Web sites or writing articles that are intended to foment or provoke terrorism."
According to Hansard, the report of proceedings in the UK Houses of Parliament, Clarke said the Foreign and Commonwealth Office and intelligence agencies are to build a database that contains details of people who provoke terrorism.
Immigration officers will have access to the database, which ministers could also use when deciding whether to exclude people from the United Kingdom, Clarke said.
Although other specific measures are yet to be announced, the government is planning changes to the law that would make it easier to deport religious extremists.
Clarke added: "Where there are grounds for considering that a person has been engaged in such activities, or will do so in the UK, exclusion will be considered. I have asked my officials together with the Foreign and Commonwealth Office and the intelligence agencies to establish a full database of individuals around the world who have demonstrated the relevant behaviours."
Late last night, several explosions hit London's transport system, exactly two weeks after more than 50 people were killed in blasts on underground railway trains and a bus, Reuters  reported.
Dan Ilett of silicon.com reported from London.