The Christian world went into mourning today for Brother Roger, founder of the Taizé religious group, who was stabbed to death during yesterday's evening prayers at his community in France.

His death in front of 2,500 young pilgrims at the Reconciliation Church turned a man many already believed to be a saint into a martyr. A 36-year-old Romanian woman, known to be mentally disturbed, is being held by police.

Today tributes from around the world poured in for Brother Roger, the 90-year-old son of a Swiss protestant pastor, who founded the community at Taizé, in the Burgundy region of France, during the Second World War when he was just 25. His motto, if he had one, was: "Love, and express that with your life."

The Archbishop of Canterbury, Dr Rowan Williams, said: "This is an indescribable shock. Brother Roger was one of the best loved Christian leaders of our time, and hundreds of thousands will be feeling his loss very personally, and remembering him in prayer and gratitude.

"But the shock and trauma for the community at Taizé will be heavy - and it will be for all the young people who witnessed this event. All of them are in our prayers."

President Jacques Chirac praised Brother Roger as "one of the most remarkable servants of the values of respect and tolerance". Chancellor Gerhard Schröder of Germany said that he regarded Brother Roger as one of the "great contemporary personalities of religious life." Herr Schröder praised him for sheltering Jewish refugees during the Second World War and fostering reconciliation in Europe.

The Rev Joel Edwards, General Director of the Evangelical Alliance said: "We are deeply shocked and dismayed to hear about the stabbing of Brother Roger. He had many friends among the evangelical community who valued his devotion to God and his selfless service to others for over half a century.

"Many people in our membership will have spent time with the Taizé Community over the years and will have drawn comfort and inspiration from being with fellow believers from around the world. Are thoughts and prayers are with those grieving at this time."

In Cologne, where hundreds of thousands of young Catholics have gathered for World Youth Day, to be attended by Pope Benedict XVI tomorrow, Prelate Heiner Koch said: "We express our deep compassion to the Taizé community."

The President of the French Bishops' Conference, Archbishop of Bordeaux Jean-Pierre Ricard, wrote to the Taizé community expressing his "deep grief" after the murder of "this great figure of a researcher and witness of God, impassioned by unity among Christians and reconciliation."

At the community today, pilgrims wandered around looking shocked and haggard at a murder that most would have considered outside the realms of possibility.

Brother Roger was awarded the Unesco prize for peace education in 1988 and wrote many books on prayer and reflection, asking young people to be confident and committed.

The spiritual leader kept a low profile, rarely giving interviews and refusing to permit any "cult" to grow up around himself. He was about to give up his community functions later this year because of his advanced age. Recently he had suffered from fatigue and often used a wheelchair.

Brother Alois, a 51-year-old German Catholic, was chosen by Brother Roger as his heir-apparent eight years ago and is now expected to return from the Catholic youth event in Cologne to take his place.