Franklin Graham has called Christians to stand against the global 'Christian genocide', saying that 100,000 believers are killed every year for their faith.

Graham, president of Samaritan's Purse and an outspoken conservative evangelical commentator, was speaking as he opened a four-day conference in Washington to draw attention to the suffering of the persecuted Church, according to Religion News Service.

'It is safe to say over than 100,000 a year are killed because of their faith in Christ. In the last 10 years that would be close to a million people. It's the equivalent of a Christian genocide,' he said.

'I am sure the number of Christians who are in prison or martyred each year would stagger our mind if we really knew what the total number really was. And it would send us to our knees in sorrow and in prayer.'

It isn't clear what Graham's figures – which the conference called a conservative estimate  –are based on.

Open Doors, which also advocates for the persecuted Church, estimates that about 4,000 are annually killed for their faith.

'In the name of tolerance, Christians are often treated with intolerance because they stand for moral purity and they stand for God's truth. In the name of patriotism, Christians are often treated as unpatriotic because they follow a higher authority, almighty God,' Graham told his audience at the World Summit in Defense of Christians.

Graham highlighted the spectre of global persecution as well as the 'threat' of militant Islam to the Church.

Around 600 people from 136 countries have gathered for the conference, which draws delegates from regions of persecution such as Egypt, Sri Lanka, India, Pakistan, South Sudan and the Central African Republic.

On Thursday the assembly will host US Vice President Mike Pence.

Other speakers opening the gathering included Metropolitan Tikhon, primate of the Orthodox Church in America, Pope Francis' US representative, and the bishop of the Episcopal Diocese of Egypt, the Rev Mouneer Hanna Anis.

Anis emphasised the power of forgiveness in the face of violent opposition.

'The forgiveness that has been expressed by families of martyrs is the most powerful witness in the face of terrorism,' he said.