Pope Benedict XVI sent his first tweet in Latin yesterday on the eve of the annual Week of Prayer for Christian Unity.

A month after sending his tweet using his personal account - @pontifex - the Pope said: "What does the Lord ask of us as we work for Christian unity?"

He answered: "To pray constantly, do justice, love goodness, and walk humbly with Him." ("Orare semper, iustitiam factitare, amare probitatem, humiles Secum ambulare".)

His tweet picked up on the theme of this year's week of prayer - a verse from the Old Testament that reads in English: "What does the LORD require of you but to do justice, and to love kindness, and to walk humbly with your God?" (Micah 6:8).

Speaking at the Angelus in St Peter's Square yesterday, the Pope said the Church "formed by human beings, is always in need of purification". He added: "One of the most serious sins that disfigure the face of the Church is the one against her visible unity, particularly the historical divisions that have separated Christians and that still have not been overcome."