At least 22 people have been killed and more than 100 wounded in a string of attacks across Iraq, officials said.
The attacks included two car bombs at a Baghdad International Airport where at least one person was killed and 12 injured.
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Five people were killed and dozens more were injured after a car and knife attack in the capital on Wednesday afternoon.
Among those expected to attend the ceremony will be former US President Bill Clinton and ex-Northern Ireland first minister Peter Robinson.
Five people have been killed and 40 injured after a car and knife attack in London on Wednesday.