Representatives of the two largest Christian bodies in the world came together on Friday evening in Rome to celebrate the centennial anniversary of the Week of Prayer for Christian Unity and close the worldwide event.

General secretary Rev Dr Samuel Kobia of the World Council of Churches - which represents some 560 million Protestant Christians - joined Pope Benedict XVI - head of the more than 1-billion-member Roman Catholic Church - for a private meeting. They later took part in an ecumenical Vespers service at the Roman basilica of St Paul Outside the Walls.

Pope Benedict XVI presided at the ecumenical service where Kobia brought greetings on behalf of the fellowship of 347 churches constituting the WCC.

The service conclude the traditional Week of Prayer for Christian Unity, celebrated January 18 to 25 in the northern hemisphere. In the Global South, churches favour the days around Pentecost to observe the Christian unity week.

The Roman Catholic Church has been part of the ecumenical event from nearly its inception.

In 1909, the Roman Catholic Pope at the time, Pius X, was approached about joining the event and ended up giving his official blessing to the effort. In 1916, Pope Benedict XV encouraged its observance throughout the Roman Catholic Church.

But it was in 1967 that members from Orthodox, Protestant and Roman Catholic Churches agreed to jointly observe a time of prayer called the Week of Prayer for Christian Unity.

Since 1968, the World Council of Churches and the Pontifical Council for Promoting Christian Unity has worked together annually to promote prayer for the unity of Christian churches during the designated week.

This year marked the 100th anniversary of the annual event celebrated by millions of Christians worldwide. The theme this year was "Pray Without Ceasing", taken from I Thessalonians 5:17.

On Friday, Pope Benedict XVI and Kobia were joined by high-level representatives from both parties for the closing day of the Week of Prayer for Christian Unity.