There has been a recent surge in violence against Christians in northern Iraq. At least three Christians have been killed near the city of Mosul this week.
A gunman opened fire on two university students on Tuesday, killing one Assyrian Christian.
Also, earlier this week, two other believers died in separate attacks.
The attacks have been linked to Iraq's upcoming parliamentary elections.
Christians make up less than three percent of Iraq's population, but radical Muslims want to isolate them and drive them from the country.
"What can we say?" asked Bishop Shlemon Warduni, the second-most-senior Chaldean bishop in Iraq.
"We are very sad. The government is looking at what is going on, it is speaking, but doing nothing," he told AFP.
Roughly half of Iraq's Christian population, about 500,000 people, has fled the country since 2003.