Clashes broke out between Muslims and Coptic Christians in Alexandria in Egypt after the funeral of a Coptic worshipper killed in church on Friday.
The funeral procession turned into a protest
Police fired tear gas and tried to separate the groups, who threw stones and attacked each other with sticks. Fifteen people were arrested.
The unrest followed the funeral of Nushi Atta Girgis, 78, who died in one of three knife attacks in Alexandria.
Christians have accused the government of failing to protect them.
Mourners shouted anti-government slogans as the funeral procession - attended by an estimated 3,000 people - turned into a protest outside the church where the funeral was held.
At least 15 people were injured and four vehicles were burned out, an interior ministry source said.
The ministry said those arrested were both Copts and Muslims and included "some fanatic extremist elements".
'Crushed by Muslims'
The government has said a "deranged" man was arrested for carrying out all the attacks at the three churches, but some Copts believe they were carried out simultaneously as part of an anti-Christian plot by extremist Muslims.
A judge has remanded the arrested man, Mahmoud Salah-Eddin Abdel-Raziq, 25, in custody.
"Certain papers speak of a madman. I don't believe a word. It is propaganda to silence us and to make us believe it is an individual incident," said Karim, a 78-year-old Copt at the funeral.
"We have always been peaceful, but we are always crushed by the Muslims," said 30-year-old Girgis Mina. "If the state does not protect us, we will do it ourselves."
Egyptian Christians - most of whom are Copts - make up 10% of the population and have complained of harassment and discrimination.
Some Copts argue that previous attacks on them have gone unpunished or have drawn light sentences.
Their church split from the Eastern Orthodox and Roman Catholic churches in 451AD because of a theological dispute over the nature of Christ, but is now, on most issues, doctrinally similar to the Eastern Orthodox church.