At least 18 people have died after two roadside bombs struck a convoy carrying Iraqi families fleeing a town controlled by the so-called Islamic State in northern Iraq.

The bombs targeted a truck carrying people from Hawija, about 120km south of Islamic State's stronghold in Mosul, as they were being taken to the town of Al Alam, next to the Tigris river.

A police spokesman said 17 of the dead were from the displaced families, while a policeman in an accompanying patrol car was also killed.

Pictures published on social media by a group linked to Iraq's defence ministry showed several victims lying closed to the remains of the truck.

Meanwhile, Iraqis fleeing Mosul reunited with their loved ones today at Khazer refugee camp in the east of the city.

Some families, who had not seen one another for more than two years, met at the site for an emotional reunion.

Men, women and children were seen hugging and kissing as many more waited anxiously outside the camp's fence.

Khazer camp's inhabitants have to stay there until they have cleared security screening and other checks.

Thousands of people have left Mosul since Iraq's regular troops and special forces - along with Shi'ite militias, Kurdish peshmerga fighters and other groups backed by US-led air strikes - launched their campaign to retake the city nearly three weeks ago.

At least 22,000 people have been displaced since the start of the Mosul offensive according to the United Nations, excluding thousands of others from nearby villages forced back to the city by retreating IS fighters who used them as human shields.

Mosul is still home to nearly 1.5 million people, who risk being caught up in brutal urban warfare.