Leaders of the World Council of Churches (WCC) have emphasized that answering the Holy Spirit's "call to conversion" is an essential part of living the life of servitude that is asked for in followers of Jesus Christ, in a message for this year's Pentecost observance.

"Jesus' disciples received the gift of the Holy Spirit that first Pentecost because they were waiting for it in trust. They were gathered together waiting, confident in God's promise," read the message from the WCC's presidents.

The group went on to explain that the initial blessing of the Holy Spirit on Jesus' disciples made them into "witnesses, messengers, people convinced by their master's message of love and truth."

"It becomes a time for the call to conversion, of putting into practice the gift received and commitment to the service of brothers and sisters," they said.

"Today, the call to conversion is more central than ever for every person who seeks to follow Jesus Christ and to discover meaning in life through serving those who suffer, whatever name their suffering may have."

Noting the recent progress that has been made against nuclear proliferation, the group said that in today's world there are a "small group of the humble who seek conversion, asking for forgiveness for faults committed in the past."

"Hope for conversion can be seen today in the steps some of the 'great' of this world have taken to repair past excesses of pride and domination. Yes, everything is possible for the one who turns to Christ and, in the power of the Spirit, tries to change the plans of those who continue to believe that peace can be bought only under threat of nuclear weapons."

"But, of course we Christians, who have been baptized in the name of Jesus Christ, must not limit our insistence on the need for repentance from the official leaders of the nations or of other public persons," they continue. "The call for repentance remains well-timed for every one of us, from every state, age, origin: repentance for our inconsistency between what we proclaim and how we behave; repentance for our little faith, for our compromises to the spirit of this world, for our inclination to be indifferent to justice, to solidarity, to sincere love and respect for every human person."

"It is with this deep spirit of repentance that we must await the coming and dwelling of the Spirit of God, in ourselves and in our local congregations. Only then shall we rediscover the face of our Resurrected Lord, the Kyrios, and be united with him, praying with humility and new dynamism."

"O, come, Holy Spirit! Transform the world!" they conclude.

Signers on the letter include Archbishop Anastasios of Tirana and All Albania; Mr. John Taroanui Doom of the Maohi Protestant Church in French Polynesia; the Rev. Dr Simon Dossou, Protestant Methodist Church of Benin; the Rev. Dr Soritua Nababan, Protestant Christian Batak Church in Indonesia; the Rev. Dr Ofelia Ortega, Presbyterian-Reformed Church in Cuba; Patriarch Abune Paulos, Ethiopian Orthodox Tewahedo Church; the Rev. Dr Bernice Powell Jackson, United Church of Christ in the United States; and Dr Mary Tanner from the Church of England.

Meanwhile, Pentecost celebrations in the Catholic Church gave special attention to the Virgin Mary this year, with Pope Benedict XVI saying that there is no church without Pentecost, and no Pentecost without Mary.

Reflecting during the service at St. Peter's Basilica, Benedict said, "There is no Pentecost without the Virgin Mary. Thus it was at the beginning, in the Upper Room where the disciples 'devoted themselves to prayer, together with some women and Mary, the Mother of Jesus, and his brothers' - as recounted in the Acts of the Apostles."

Benedict also declared that the church must always be universal, and be "the home of all in which each person can find himself again."

"This, in effect, is the work of God: unity; therefore unity is the sign of recognition, the 'business card' of the Church in the course of its universal history," the Pope said, noting that the unity of the church is of a "different type" than the political ties of the world, and is a unity that "aspires to cross all human borders."

Benedict also explained the difference between the fire of the Holy Spirit, which is a "flame that burns but doesn't destroy," and the fire of war and bombs, which are "lit by dictators of every age…who leave the land burned behind them."