Bishop Kirollos of the Nag Hammadi Diocese told The Associated Press that six male churchgoers and one security guard were killed.
He said he was concerned about violence on the eve of Coptic Christmas, which falls on Thursday, because of previous threats following the rape of the 12-year-old girl in November.
He got a message on his mobile phone saying: "It is your turn."
"I did nothing with it. My faithful were also receiving threats in the streets, some shouting at them: 'We will not let you have festivities'," he said.
Kirollos said he ended his Christmas Mass one hour earlier than normal because of the threats.
|The attack happened in the town of Nag Hammadi in southern Qena province
He said Muslim residents of Nag Hammadi and neighbouring villages had rioted for five days in November and torched and damaged Christian properties in the area after the rape.
"For days, I had expected something to happen on Christmas day," said the bishop, adding that police had told him to stay home for fear of further violence.
The bishop said he had an idea of who the attackers were, calling them "Muslim radicals".
"It is all religious now. This is a religious war about how they can finish off the Christians in Egypt," he said.
Christians, mostly Coptic, account for about 10 per cent of Egypt's 83-million predominantly Muslim population.