Services have been held across the UK for tsunami victims, as church leaders say it could test the faith of many.
The Queen attended a church service at Sandringham
Catholic and Anglican leaders said many would question how God could allow such disasters to happen, but said people would rely on their beliefs to cope.
Seven ambassadors from some of the worst-hit countries addressed a Hindu service in Neasden, north London.
Prayers were said at Liverpool's Catholic Cathedral and at a Sandringham service, attended by the Queen.
She was greeted by a crowd of 300 outside the entrance before attending a service addressed by the Bishop of Norwich, the Right Reverend Graham James.
A multi-faith service also took place at St Mary's Cathedral, in Edinburgh.
Sikhs, Muslims, Hindus and Buddhists joined Christians at a Catholic Mass celebrated by Cardinal Keith O'Brien.
The Archbishop of Canterbury, Dr Rowan Williams, said the disaster, in which at least 124,000 have died, could well test people's faith in God.
The official death toll of Britons stands at 40, after five more deaths were confirmed by the Foreign Office on Sunday, but many more are still missing.
Writing in The Sunday Telegraph, Dr Williams, the head of the Church of England, said: "The question: 'How can you believe in a God who permits suffering on this scale?' is... very much around at the moment, and it would be surprising if it weren't."
But he said the "extraordinary fact" was that belief survived such tests.
Dr Williams concluded that Christians must focus on "passionate engagement with the lives that are left".
The leader of the Roman Catholic Church in England and Wales, Cardinal Cormac Murphy O'Connor, echoed Dr Williams' sentiments.
He admitted that the disaster posed "a challenge to faith", but added that "it does not take faith away because we still believe in God and that he created this world".
And the Catholic Archbishop of Birmingham, the Most Reverend Vincent Nichols, in his sermon at St Chad's Cathedral, said: "Disasters do not wipe out faith anymore than they wipe out love.
"Rather, the light of love, the light of God glows more persistently in that awful darkness.
HOW TO DONATE
The Disasters Emergency Committee (DEC) is an umbrella group of UK aid charities including, among others, British Red Cross, Cafod, Oxfam, Save the Children, Tearfund
Call them on 0870 60 60 900 or donate online at www.dec.org.uk
Cash or cheques - made payable to the DEC Tsunami Earthquake Appeal - can be donated at High Street banks.
Cash or cheques (made payable to Post Office Ltd) can be donated over the counter at Post Office branches.
Other bodies raising money include the Muslim groups Muslim Aid (020 7377 4200) and Islamic Relief (0121 622 0622) and the Hindu charities Sewa International 0116 261 0303 and the ISKCON Disaster Appeal on 01923 856848.
Sri Lankan organisations including Asia Quake Relief Appeal UK (email firstname.lastname@example.org) are also raising money
"It shines in human heroism, generosity, selflessness and courage."
The Hindu prayer meeting was held at the BAPS Shri Swaminarayan Mandir Hindu temple in Neasden, north London on Sunday evening.
BBC correspondent Denise Mahoney said it was a "moving and sombre occasion".
The ambassadors of India, Bangladesh, Sri Lanka, Indonesia and Thailand were among those telling stories of courage, devastation and human tragedy, and appealing for more help.
Meanwhile, a Save the Children aid flight left the UK's Stansted airport for Sri Lanka on Sunday.
The plane is loaded with 30 tonnes of aid, including water purification tablets for three million litres of water, three generators, 10,000 tarpaulins and tents to be distributed in southern and eastern areas of the country.
And an off-road vehicle will be included to distribute aid to 37,000 families in the worst affected areas.
The plane was due to arrive in Colombo, the Sri Lankan capital, around 2330 local time.
Save The Children emergency supplies manager Adrian Uden said: "It's vital people get aid. If they don't they will die.
"They need aid, clean drinking water, shelter, the hospitals need power. Although our work is child-focused, our supplies are for everyone."
0207 008 0000 - for information on friends and relatives
0870 6060290 - for flight details or travel advice
The UK branch of Save The Children has been allocated £400,000 for its aid effort by the government, which is also funding the cost of Sunday's flight.
Prime Minister Tony Blair has called the tsunami a "global catastrophe" and the British public has responded by donating £60m to an appeal fund.
In London, the Sri Lankan High Commission in Hyde Park Gardens has been overwhelmed by donations of clothes and blankets for tsunami victims.
They are asking people not to send any more, but say money and medicines are still needed.
A telephone support line for those directly affected by the tsunami has been set up on 0845 054 74 74.