U.S. and Iraqi security officials say four separate attacks in the northern city of Mosul and in the capital, Baghdad, Sunday killed at least 16 people and wounded more than 50 others.

Officials in Mosul say a suicide car bomber struck a U.S. patrol. There were no American casualties, but the blast killed five Iraqis - including three young boys - and wounded 12 others.

Hours later, another suicide car bomber targeted an Iraqi police patrol in the city, wounding 25 people.

In a predominantly Shi'ite Bayaa district southwest of Baghdad, a car bomb killed at least nine people and wounded 13 others.

And, snipers in the western Baghdad area of Mansour killed two Iraqi soldiers.

Meanwhile, Iraqi Prime Minister Nouri al-Maliki ordered an investigation into a recent series of attacks against Christians in Mosul.

Following talks with Christian officials, Mr. Maliki condemned the violence that has prompted nearly 1,000 Christian families to flee the city recently.

Iraqi authorities have deployed more than a thousand police officers to guard Christian districts and churches in Mosul.

It is not clear who was behind the attacks, but Iraqi Christian leaders say the minority community is facing a killing campaign.

Some information for this report was provided by AFP and AP.