DUBAI, United Arab Emirates  Thousands of enraged Christians clashed with the police in Egypt on Thursday in response to a drive-by shooting the night before that left six Christians dead and nine wounded.

The attackers, who are still at large, had opened fire on several groups of Christians gathered to celebrate Coptic Christmas in the southern Egyptian city of Nag Hammadi, the Interior Ministry said in a statement.

The killings seemed to be an act of revenge tied to accusations in November that a Christian man raped a Muslim girl, the statement said.

Clashes between Muslims and Christians have grown increasingly common in recent years, especially in Upper Egypt, where there is a large Christian population and a strong culture of vendetta killings. Those killings typically spring from unexceptional disputes that spiral into full-blown conflicts that have to be settled by security forces. There are no official statistics on the size of the Christian minority in Egypt, but the generally accepted figure is 10 percent of the population.