Three Yazidi sisters were reunited this week after more than three years since they were taken by Islamic State militants.

The operation to liberate the Iraqi city of Mosul marks the beginning of the end of the Islamic State group's so-called caliphate in Iraq, the U.N. envoy for the country told the Security Council on Wednesday.

Artillery shelling thundered across Mosul Saturday as snipers traded fire from rooftops and civilians emerged from the front lines waving white flags.