Daesh terrorist group has executed 20 civilians for attempting to flee Mosul, now the target of a major military offensive, an Iraqi army officer said Wednesday.

The civilians were captured by Daesh militants on Tuesday while trying to flee Daesh-held areas in western Mosul by boat, Brigadier-General Kazim al-Maksusi told Anadolu Agency.

"The men were immediately executed by Daesh militants, while women and children were taken hostage," he said.

Meanwhile, al-Maksusi said some 55 civilians have managed to flee Daesh-held parts in western Mosul to the army-seized areas in the city's northern part.

Mosul is currently the target of a wide-ranging army offensive aimed at recapturing the city -- once considered Iraq's second largest in terms of population -- from the terrorist group.

Late last month, the army announced the "total liberation" of eastern Mosul following three months of fighting.

Daesh overran Mosul, along with vast swathes of territory in northern and western Iraq, in mid-2014.