"The cycle of violence, provocations and retaliations which we have witnessed In Iraq over the past few weeks has to stop," former Belgian premier Charles Michel said.

"Further escalation must be avoided at all cost," he added, hours after a US strike killed Iranian covert force commander Qasem Soleimani at Baghdad airport.

Michel did not refer directly to the US strike, but noted the role of Iraq's militias -- many of them supported by Soleimani's Quds Force -- in the unrest.

"Iraq remains a very fragile country," he said. "Too many weapons and too many militias are slowing the process towards a return to normal daily life for Iraq's citizens.

"The risk is a generalised flare up of violence in the whole region and the rise of obscure forces of terrorism that thrive at times of religious and nationalist tensions."