The Egyptian army has managed to persuade a few people to leave the al-Fath mosque in central Cairo, escorting them through the angry anti-Muslim Brotherhood crowds outside.
Negotiations are ongoing to try and get the remaining people, estimated at around 400, to leave peacefully.
Those inside want assurances they will not be set on by the crowds outside, and do not risk arrest or detention before they agree to leave.
They fled into the mosque late on Friday to escape the spiralling violence in the surrounding streets, although the police have claimed they subsequently came under fire from the mosque.
On Saturday morning the police arrived to seal off the building and push back the anti-Morsi crowd from the entrance. The mosque is on Ramses square, the scene of the worst violence in the capital on Friday. Many bodies and injured people were already in the mosque before the siege began.