Church leaders have expressed their gratitude for the life and service of Queen Elizabeth II, Britain's longest-serving monarch, after her death today aged 96.

The Queen died peacefully at her Scottish estate at Balmoral this afternoon, a statement by Buckingham Palace said.

Members of the royal family travelled to Balmoral today to be by her bedside after doctors decided to keep her under medical supervision over concerns for her health.

"The Queen died peacefully at Balmoral this afternoon," an official statement reads.

"The King and The Queen Consort will remain at Balmoral this evening and will return to London tomorrow."

Church leaders have joined in the outpouring of tributes being paid to the Queen.

The Archbishop of Canterbury, Justin Welby, expressed his "profound sadness" at her passing.

"My prayers are with the King and the Royal Family. May God draw near them and comfort them in the days, weeks and months ahead," he said.

"As we grieve together, we know that, in losing our beloved Queen, we have lost the person whose steadfast loyalty, service and humility has helped us make sense of who we are through decades of extraordinary change in our world, nation and society."

In his statement, the Archbishop thanked the Queen for her "extraordinary dedication" to the UK, her realms and the Commonwealth.

He also praised the Queen's Christian faith which he said had "spoken powerfully of the light that no darkness can overcome" during "the darkest days" of the pandemic.

"Even as the late Queen mourned the loss of her beloved husband, Prince Philip, we saw once again evidence of her courage, resilience and instinct for putting the needs of others first – all signs of a deeply rooted Christian faith," he said.

"As a faithful Christian disciple, and also Supreme Governor of the Church of England, she lived out her faith every day of her life. Her trust in God and profound love for God was foundational in how she led her life – hour by hour, day by day," he continued.

"In the late Queen's life, we saw what it means to receive the gift of life we have been given by God and – through patient, humble, selfless service – share it as a gift to others.

"Her late Majesty found great joy and fulfilment in the service of her people and her God, 'whose service is perfect freedom' (BCP).

"For giving her whole life to us, and allowing her life of service to be an instrument of God's peace among us, we owe her a debt of gratitude beyond measure."

The Archbishop of York, Stephen Cottrell, said, "Throughout her long reign, and in all the confusions and challenges of a changing world, Her Majesty has been a constant, faithful presence." 

He continued, "In Her Majesty's first Christmas broadcast, ahead of her Coronation she asked the nation, whatever their religion, to pray that God would give her wisdom and strength to carry out the solemn promise she would be making and to faithfully serve God and us all the days of her life.

"That is most definitely a prayer that has been answered. Her service to our nation and Commonwealth has been exemplified by her devotion to her duty, which has always been offered with joy. Underpinning this has been her deep faith in God and in her we have witnessed God's faithfulness at work.

"Her Majesty leaves a remarkable legacy which not only lives on in this country, but stretches across the Commonwealth and the rest of the world. Her desire to bring people together and use her role to build up communities and wider society has been a cornerstone of her reign." 

Archbishop Cottrell invited people to join him in praying for the royal family in the coming weeks and for King Charles III and "the responsibilities that now rest upon him".

Cardinal Vincent Nichols, head of the Catholic Church in England and Wales, said he was "heartbroken" by the Queen's death but also "so full of admiration" for her unfailing service and devotion to her people over the last 70 years.

"Even in my sorrow, shared with so many around the world, I am filled with an immense sense of gratitude for the gift to the world that has been the life of Queen Elizabeth II," he said.

"At this time, we pray for the repose of the soul of Her Majesty. We do so with confidence, because the Christian faith marked every day of her life and activity."

The Queen's death falls within her Platinum Jubilee year after reaching the milestone of 70 years on the throne.

She had appeared increasingly frail in recent times as public appearances became rarer. Mobility issues led to her significantly scaling back official duties and using a walking stick for support.

During celebrations for her Platinum Jubilee over the summer, she was forced to pull out of a thanksgiving service at St Paul's Cathedral after experiencing discomfort during a parade and flyover.

Earlier in the year, she cancelled her attendance at the Maundy Thursday church service for the first time since 1970 and was absent from the traditional family outing to church on Easter Sunday.

The Queen's official titles included Supreme Governor of the Church of England and Defender of the Faith but she was a committed Christian and frequently used her annual Christmas Day speeches to share her faith.

Evangelist J John said: "It is salutary to read the words of the Queen's coronation service and see all that, so long ago, she promised to defend for the nation and the church. At the end of that long life, we can say with appreciation that she fulfilled her vows and did what she promised. She kept the faith."

The London Institute for Contemporary Christianity (LICC) said: "We thank God for the extraordinary life and witness of HM Queen Elizabeth II. May she rest in peace and rise in glory. We pray for the King, Queen Consort, and Royal Family. Lord, comfort them. Be with all who grieve. And give us strength to face this day and those ahead."