There is a "move of the Spirit going on", according to the Archbishop of Canterbury – and it's centred on prayer.

Speaking at the launch of the 2017 Thy Kingdom Come prayer campaign, he referred to the astonishing success of last year's initiative.

Expected to involve around 5,000 people, it was supported by 20 times as many - around 100,000.

The campaign involves encouraging individuals, families and churches to pray for evangelism between Ascension and Pentecost, May 25 to June 4. This year more resources have been produced and "beacon" events planned at cathedrals and other venues to attract large numbers of people.

Archbishop Justin Welby said at Lambeth Palace this morning: "When the wind of the Spirit is blowing, hoist the sails."

He said Thy Kingdom Come was not a Church of England event, "any more than someone who starts an avalanche can say, 'That's my avalanche.'"

The initiative has been adopted by the World Methodist Conference, the Salvation Army and the Roman Catholic Church, and at a meeting in Istanbul earlier this week Ecumenical Patriarch Bartholomew gave it his blessing.

Welby said: "Everyone is doing it their own way. Just pray, between Ascension and Pentecost, for the work of the Spirit, that we will see God opening people's hearts to receive the good news of Jesus."

He spoke of the importance of relying on God and "knowing you haven't got what it takes to do something". He reflected movingly on an experience two years in a refugee camp in the Democratic Republic of Congo where all support had been withdrawn, describing it as "a most terrible place".

He described spending time in a tent with disabled children who had been abandoned by their parents, a place of "absolute horror"; when he came out he was asked by the local bishop to speak some words of encouragement. Feeling he had nothing to say, he quoted the verse "Jesus Christ is the same yesterday, the today and forever."

"They all started singing and applauding," he said. "I thought, Oh, that's God doing that. I was going to give practical solutions, but they wanted someone to remind them that God doesn't change."

He said: "None of us have the resources to bring people to faith in Jesus Christ. The cupboard is bare. But the task is set before us by Jesus himself, who says, 'You are my witnesses.' We are to be Jesus in the world."

Welby said: "I cannot remember anything I've been involved in when I have sensed so clearly the work of the Spirit."

He concluded: "We pray many prayers not knowing how they will be answered. But when we pray, 'Come, Holy Spirit', we know he will move in a way that points people to Jesus Christ."

Resources for the campaign can be found on the Thy Kingdom Come website, including a Pledge2Pray page showing an interactive map which lights up the locations throughout the world where prayer is taking place.