British police have already identified the people they want to target under the proposed new anti-terrorism measures, Metropolitan Police Commissioner Sir Ian Blair said.
The officer said he was "very pleased" with the measures and that they fulfilled most of the requests for new powers made to Prime Minister Tony Blair by the police last week.
Nearly a month after the London suicide bombings, Tony Blair announced on Friday, the banning of two extremist organisations and unveiled stringent measures to clamp down on terrorism, including deportation of those who incite hatred.
UK to change deportation laws
He said a list would be drawn up of extremist websites, bookshops and centres, involvement with which, would prompt the home secretary to consider deportation of any foreign national. There would be new anti-terror legislation in the autumn, including an offence of condoning or glorifying terrorism which would apply anywhere, not just in the United Kingdom.
Sir Ian told BBC television on Friday, "What we are looking for are the people who are influential in spreading hate -- that's the key. We certainly aren't attempting to go after everybody who has got an opinion with whom we disagree."
When asked if police had identified mosques which could be closed down for "formenting extremism", he said, "I'm not aware of any specific mosques in mind, but there certainly are some specific people in mind. We will examine each case carefully and then take the necessary action."
A third terror strike on London remained likely, but not certain, he added.