The UK's Muslim community must help London's police in the fight against terrorism, the Met Police Commissioner Sir Ian Blair has said.
Blair said the community must work together
Speaking at a the Minhaj-ul-Quran Mosque in Forest Gate, East London, he appealed to worshippers: "I need you".
"We have got nearly 1m Muslims in London, 1.6 in the UK," he said.
"We've only got 300 Muslim police officers in London - that's not good enough. I need your mothers, fathers, sons and daughters."
"We must seize this moment, this weekend, next week.
"We have to seize a moment in which the Muslim community in Britain changes from your position of shock and disbelief into active engagement in counter-terrorism."
The attacks were not anything to do with Islam, he said, but were done in the name of Islam "and that puts the responsibility on all of us".
"There's nothing wrong with being a fundamentalist Muslim, Jew or Christian, the key issue is the slide into extremism," he said.
He compared the "perversion of the virtues of Islam" behind the London "atrocities" to anti-abortionists in America who shoot doctors.
"For you I know this is the worst nightmare that can happen to the British Muslim community," he said.
"But the police service is engaged with your leaders to reach out to you."
It was not the police or intelligence services that would defeat terrorism, he said, but communities.
On taking office earlier this year, he said he changed the Met Police logo to "Working together for a safer London" because the police and community could only succeed together.
That was borne out in the past when police began to work with the Afro-Caribbean community to solve Yardie murders.
"You cannot let the men of violence win," he told them.
"We know only four people did this. I can't prevent four people attacking a tube system that carries 3m people a day.
"I can't do it - you might be able to do it; collectively London can do it because we are the most diverse city on the planet."
Sir Blair went on to visit a Sikh temple in Manor Park, also in East London, were he was told of the community's concerns following the London attacks.
'Race hate crimes'
Jagta Singh, of the political party Sikh Federation (UK), said: "Sir Ian spoke to us to give us reassurance following the attacks on Sikhs after last Thursday's terrorist attacks."
Mr Singh said Sikhs were "the largest and most visible" ethnic minority in London, which put them "at the greatest risk of race hate crimes".
At the meeting he presented Sir Ian with a memorandum outlining the concerns of the Sikh community in the UK.
Mr Singh said attacks against Sikhs were "spreading and increasing in seriousness", including a knife attack reported in Ireland.
"We have had numerous reports of race hate crimes targeting Sikh taxi drivers, bus drivers and even tube workers that interact with the public in providing essential services," he said.
He added that Sir Ian was also presented with a 'kirpan', a 3ft sword symbolising justice.