"The month of April was the deadliest since June 2008. A total of 712 people were killed and another 1,633 were wounded in acts of terrorism and acts of violence," a statement from the UN mission in Iraq said on Thursday.

"Baghdad was the worst-affected governorate, with a total of 697 civilian casualties (211 killed, 486 injured), followed by Diyala, Salaheddin, Kirkuk, Nineveh and Anbar," the statement added.

A wave of violence began on April 23 when militants invaded security checkpoints near the town of Hawijah in north Iraq, sparking clashes in which 53 people were killed.

Dozens more died in subsequent unrest, including attacks targeting security forces in Kirkuk, Nineveh, Diyala and Anbar provinces, raising fears of a return to the all-out conflict that took the lives of tens of thousands of people from 2006 to 2008.

The late-April violence was the deadliest so far linked to protests that broke out in the country more than four months ago.