Muslim leaders have condemned the terror attacks on London and called for full co-operation with police.
Muslim women in headscarves are warned to be vigilant
Muslim Council of Britain spokesman Inayat Bunglawala called on worshippers to pray for victims at Friday prayers.
And Ahmed Sheikh, president of the Muslim Association of Britain, said he feared a backlash and added that the Muslim community would feel less safe.
He warned that Muslims, especially women in headscarves, might fall prey to vigilante attacks.
Home Secretary Charles Clarke said he would be working closely with different groups to prevent any attacks on British ethnic minorities.
"I'm hoping to meet faith leaders later today [Friday] to discuss some of these questions and the police are looking very, very carefully at any organisations that might try and attack particular ethnic minorities," he told BBC Radio Five Live.
Muslim News editor Ahmed Versi noted one of London's biggest Muslim areas, around Aldgate, had been targeted.
Mr Sheikh said the unique good relationship Muslims had with the government and society was threatened.
"The person who did this was targeting along with wider British society the Muslim community, ruining the good relationship we have."
He said the police should consider extra protection for mosques and Islamic schools and said Muslims, particularly women in headscarves, should be vigilant and avoid unnecessary journeys.
"It is scary. A tiny element of the community will make use of this. It is a blow to us, to all of us. It is a moment of sadness and we send our condolences to the families of those who have been killed or injured."
Sir Iqbal Sacranie of the Muslim Council of Britain said he utterly condemned the attacks.
"We are simply appalled and want to express our deepest condolences to the families.
"These terrorists, these evil people want to demoralise us as a nation and divide us.
"All of must unite in helping the police to hunt these murderers down."
Mr Sacranie admitted "there may well be elements who want to exploit this tragedy and incite hatred".
Faith leaders in the East End have prepared for the aftermath of a terror attack in London.
The Bishop of Stepney, Stephen Oliver and Dr Mohammed Abdul Bari, the chairman of the East London Mosque, spoke together outside the Royal London Hospital saying the East End and London must remain united in the face of terror.
Dr Bari said "We're just shocked and horrified by what has happened. I spoke to the congregation at the mosque and tried to calm their fears and told them they must remain vigilant.
"We have worked together with the communities in the East End for many years and we must continue doing so."
Bishop Oliver said: "When something like this happens people are at first afraid, and then people get angry.
"There's a great deal of speculation in this atmosphere. We are determined that whatever the reaction it is one that unites the different faith communities."
Mr Versi said he had already received one threatening e-mail about the blasts.
"There might be some increase in attacks on the Muslim community especially visible aspects of Islam like mosques, community centres and women with headscarves.
"Recently there have been a lot of attacks on Muslim women on buses in London, it has increased during the last few months."
But he said the immediate Muslim revulsion at the attacks could help calm the situation.
"I don't think there'll be as high a number of attacks as after 11 September because Muslims have come out very strongly, especially Muslim leaders, condemning the attacks.
"I'm sure many Muslims will have been injured as well... one of the bombs - at Aldgate - was near to the east London mosque, it's a very heavy Muslim area.
"Muslims have to be vigilant now, especially the mosques, and I hope the police will increase security on mosques and Islamic centres."
Other religious leaders also offered their condolences and condemned the attack.
Chief Rabbi Sir Jonathan Sacks said: "These terrible events have brought home to us the full evil that terror represents.
"It is not the weapon of the weak against the strong but the rage of the angry against the defenceless and innocent. It is an evil means to an evil end."
The Sikh Federation said: "We totally condemn the terrorist attacks targeting innocent civilians in London. These are the acts of cowards and a challenge to the international world. Those responsible have no respect for human life."
The federation is cancelling a demonstration due to be held on Friday outside the Indian High Commission.