By Heba Saleh
BBC News, Cairo
Hundreds of Egyptian Christians have been protesting at the Coptic Orthodox cathedral in Cairo.
Relations between Christians and Muslims are occasionally tense
Demonstrators hurled stones at policemen after they sealed off the cathedral.
The protest were provoked by rumours that the wife of a priest in a town in northern Egypt had been pressured to convert to Islam.
Coptic Christians form an estimated 10% of the country's population and often complain of discrimination.
The protestors have been in the main Coptic cathedral in Cairo since Saturday.
They are angry at the disappearance of the wife of a priest in a village in the Delta who is rumoured to have been forced to convert to Islam.
There is no exact information as to the whereabouts of the woman and no one is certain whether she left her home willingly or under pressure.
Priests have been urging the protestors to stay calm, but some have hurled stones at policemen who have sealed off the cathedral.
The Egyptian authorities have promised to locate the woman and restore her to her family.
Although relations between Christians and Muslims in Egypt have been generally peaceful, there have been periodic eruptions of sectarian violence, especially in upper Egypt.
More generally, however, Copts complain that they often face discrimination and that they are vastly under-represented in senior government positions and in the army and the police.
Also, allegations of forced conversions surface every year.
The rise of an assertive Islamist movement in Egyptian society in the last three decades has produced tensions in Coptic-Muslim relations.