By Matt McGrath
BBC science correspondent
The cave is beneath the ancient church of St Georgeous
Archaeologists in Rihab, Jordan, say they have discovered a cave that could be the world's oldest Christian church.
Dating to the period AD33-70, the underground chapel would have served as both a place of worship and a home.
It is claimed that it was originally used by a group of 70 persecuted Christians who fled from Jerusalem.
These early Christians lived and practised their faith in secrecy until the Romans embraced Christianity several hundred years later.
Rihab is in Northern Jordan. The cave is beneath the ancient church of St Georgeous, itself one of the oldest known places of worship in the world.
According to Dr Abdul Qader Al-Hassan, the director of the Rihab Centre for Archaeological studies, the cave site shows clear evidence of early Christian rituals that predate the church.
Dr Al-Hassan says that steps lead down into the chapel which is approximately 12m long and seven metres wide.
There is a circular area of worship with stone seats separated from living quarters. This circular element, called an apse, is important says Dr Al-Hassan because there is only one other example of a cave with a similar feature, which was also used for Christian worship.
Dr Al-Hassan said: "We found beautiful things. I found the cemetery of this church; we found pottery shards and lamps with the inscription 'Georgeous'".
In the cave there is also a tunnel that leads to a cistern which supplied water to the dwellers. An inscription in the floor of the church above refers to the "70 beloved by God and the divine" whom the archaeologist believes were refugees from religious persecution in Jerusalem.
Dr Al-Hassan says that excavation of the tunnel and the cistern may yield yet more evidence about the lives of these early Christians.
"From the tunnel to the cistern is very important. We want to clean it and make an excavation inside it. We found a very old inscription beside it and coins also, and crosses made from iron."
Other experts say they are cautious about the claim. They want to examine the artefacts and see clear dating evidence. The earliest confirmed examples of churches date from the third century, they say.