Pope Francis on Wednesday appealed for a concerted effort to protect civilians Iraq caught in the ongoing bloody war in their nation and offered special prayers for those trapped in the embattled city of Mosul.

Voicing deep pain for the victims of the deadly conflict in Iraq, Francis appealed to all sides to make every possible effort to protect civilians, which, he said, is an "imperative and urgent" obligation, Vatican Radio reported.

The Pope's appeal came at the end of his catechesis during his weekly general audience in St Peter's Square attended by some 13,000 pilgrims.

Iraqi forces backed by US-­led coalition air strikes are trying to dislodge militants from the Islamic State jihadist group in Mosul – Iraq's second city – where the US ­led coalition allegedly had a role in a bombing which killed over 200 people earlier in March.

US Central Command is investigating one of the deadliest single incidents of the Mosul siege, when up to 240 civilians allegedly died in a bombing in Mosul's Jadida district on March 17.

Thousands of Iraqi civilians have died in the fighting since the military offensive to retake Mosul began in mid-October, over 200,000 have been left homeless and the United Nations estimates that several hundred thousand remain trapped in IS-held areas of the city.

Francis called on the Iraqi people to unite while respecting diversity and asked Catholics to pray for reconciliation and harmony between Iraq's various ethnic groups, Vatican Radio said.