Oxfam reported the first hour of its appeal had raised more than £50,000.
The Queen sent a message to Pakistan's president today expressing her " heartfelt sympathy" at the devastation, a sentiment echoed by Prime Minister Tony Blair in a message and subsequent telephone call to General Pervez Musharraf.
In her message to General Musharraf, the Queen said: "I was shocked to hear of the devastating earthquake which has caused such destruction and loss of life in Pakistan. I send my heartfelt sympathy to you and the people of Pakistan, especially to the bereaved and injured and all who have been affected by this terrible disaster."
Prime Minister Tony Blair promised that the the UK stood ready to provide more assistance "as and when required".
He said: "We are immensely proud of our close ties to Pakistan, made even closer by the large population of British citizens, who trace their origins to the Kashmir region. Such ties make the growing number of casualties even harder to bear."
Muslim charities including Muslim Aid, Islamic Relief, Kashmir International Relief Fund and Muslim Hands were among the first to mobilise appeals for the homeless or injured. They were joined by charities including Oxfam and Unicef UK, which set up relief teams and sent tents, clothes and medicines to the troubled regions.
The Muslim Council of Britain said more than £3m would be collected from mosques as the shocked community prayed during Ramadan. Sir Iqbal Sacranie, its secretary general, said: "All major mosques in the country have launched appeals in their local areas. We have been hearing that hundreds of families in the UK have found out their close relatives, their dear ones, children of relatives, have suffered from the tragedy ... so it is not people in another part of the world.
It is their own ones who are suffering." He added: "My estimate today was, by this evening, we would be getting from the mosques of the country in excess of £3m, but it will go higher."
Muslim Aid, which had initially pledged £100,000, had increased the amount to £250,000 yesterday, after receiving £150,000 from the public. Ebrahim Sa Mohamed, the charity's chief executive, said: "A lot of people are ringing in and offering anything ranging from £3,000 to £1."
The charity provided 300 tents and 1,200 blankets, along with its partner organisation, Khidmat, as well as arranging for water tanks and sanitation facilities in Kashmiri regions. A longer-term rehabilitation programme was launched with house rebuilding and "suitable livelihood" initiatives under way, providing homes and jobs for survivors.
Parveen Khan, from the Kashmir International Relief Fund, said the organisation had gathered thousands of pounds from donations. Oxfam was offering about 60,000 tents and 300,000 blankets, jerry cans and hygiene kits
How to make a donation
Donations for the relief efforts in the devastated region are being collected by the following agencies:
To give to the British Red Cross appeal, visit www.redcross.org.uk/asianearthquake, call 08450 535 353 or write to British Red Cross Asian Earthquake Appeal, Freepost, LON18968, Sheffield, S98 1ZA.
To donate to Oxfam's appeal, go to www.oxfamorg.uk or give donations at Oxfam shops or phone 0870 333 2500.
To donate to Unicef UK's fund, call 0800 037 9797 or 08457 312 312, or visit www.unicef.org.uk
Muslim Aid is on 020 7377 4200 or can be contacted at PO Box 3, London, E1 1WP or at www.muslimaid.org