A crowd of Egyptian Muslims angered by rumours a woman had converted to Christianity clashed with police on Friday outside the church where they believe she has taken shelter, security sources said.
The disturbances outside the church in Kom Ombo near Aswan, around 1,000 km (620 miles) south of Cairo, were the latest case of a rumoured conversion sparking strife between Christian and Muslim communities - an incendiary issue that has often fed sectarian tensions here.
More than 20 riot police trucks deployed outside the church, and the crowd threw rocks at officers who returned fire with tear gas, state news agency MENA reported.
The family of Sahar Touni, 36, who disappeared three days earlier, have told security forces they may storm the church unless she is found in seven days, the sources said.
It was not possible to confirm whether Touni was in the church.
Incidents of Christian-Muslim strife have increased in Egypt, an overwhelmingly Muslim nation with a Coptic Christian minority of about 10 percent, since the uprising that toppled Hosni Mubarak in 2011. This gave freer rein to hardline Islamists repressed under the ousted president.
President Mohamed Mursi, a Muslim Brotherhood politician elected last year, has promised to protect Christian rights.