Baghdad - Two Christian sisters were killed Wednesday and their mother was injured in a house raid in the northern-Iraqi city of Mosul, a police source said.

Unknown gunmen shot one sister in front of her house in the al- Qahera district in northern Mosul. The woman, a government employee, was waiting for a bus to take her to work, the source told the Voices of Iraq (VOI) news agency.

The armed men shot and killed one of the two sisters in front of her house while she was waiting for the bus and then stormed the house and opened fire on the family, killing the other sister and injuring their mother, who was rushed to a nearby hospital for treatment," the source said.

The gunmen planted a bomb inside the house which went off injuring three policemen who entered the house after the killings.

The gunmen had attempted to set the house ablaze, the source said.

Christians in Mosul had been subjected to killings and death threats since September, and many thousands have fled the city. (dpa)