Believers in the Holy Land are worried after a leaflet threatening attacks from Muslim jihadists was handed out in the Israeli capital.
The document has been found in the east of Jerusalem and appears to threaten "revenge" on Christians.
It is signed by a group calling itself "ISIS [Islamic State] Palestine".
"Vengeance" will be brought upon followers of Christ, the leaflet said.
Nashat Filmon, from the Palestinian Bible Society, said the threat was real.
He said: "Everything is expected from ISIS [Islamic State], as we saw in the Middle East many Christians have been killed, been displaced as a result of the presence of ISIS, you know in Mosul more than 150,000 people had to leave this historical Christian place and city and go and be scattered all over.
"So we know that Isis does kill, does threaten and does have an extended hand, I mean this could be very real."
Recent figures suggest there are 12,000 Christian residents in Jerusalem, and many more Christian tourists every year.
It's thought a large number of Palestinians have left the area to go and fight for Islamic State in Iraq and Syria, although there is no way to verify this.
IS has made vocal attacks on the Christian faith in the past, with one its magazines even showing the group's black flag flying above the Vatican.
Nashat Filmon added that he thought Islamic State was active in Jerusalem.
He said: "There have been calls for prayer, there have been calls to stand against these threats and to fight it back by every peaceful means.
"The church is also addressing the issue by encouraging its people to stay strong in the faith and of course to be thankful, to praise God.
"Just around us people have been killed, people have been displaced not far away from us, two hours drive people have been and continue to be killed so we are in a much better position.
"We need to remember God's grace and God's protection, not to take anything for granted but to trust the Lord will keep us safe in these difficult moments."