Daesh militants have massacred 200 civilians in Iraq's northern city of Mosul, an Iraqi lawmaker has claimed.

MP Intisar al-Jabouri told Anadolu Agency on Sunday the victims had been detained and killed for refusing to fight alongside the Daesh group against Iraqi forces.

The lawmaker's claim could not be verified by independent sources.

Last week, the Iraqi army, backed by U.S.-led coalition airstrikes, launched a much-anticipated offensive to retake Mosul, the last Daesh stronghold in northern Iraq.

The terrorist group captured Iraq's second largest city in mid-2014 before overrunning large swathes of territory in the country's northern and western regions.

The Iraqi army, backed by local allies on the ground and a U.S.-led air coalition, has since retaken much of the territory. Nevertheless, the terrorist group remains in control of several parts of the country, including Mosul.