An army captain has told Reuters that gunmen used machine guns and hand grenades in an attack on a military post near Dhuluiya, 70 km (45 miles) north of Baghdad.
More top news
Over 40,000 people picked up their packs to take part in the annual marathon in the capital.
The country's voters are concerned about security, the economy, and the 10% unemployment rate.
A pregnant woman and a man suffered "severe discomfort" after someone threw bleach at them from a passing car, hitting them in the eyes.