The Islamic State (Isis) executed civilians in western Mosul who were trying to flee to the liberated eastern side of the city, where formerly displaced citizens continue to return.

An Iraqi army official told Turkish state-run news agency Anadolu that 20 people were killed by Isis militants, who still control the part west of the Tigris river in Iraq's second largest city. "The men were immediately executed by Daesh militants, while women and children were taken hostage," Brigadier-General Kazim al-Maksusi said, referring to the terror group by its Arabic acronym.

The brigadier-general also said that 55 people were able to flee to the other side of the river, controlled by the Iraqi forces.

In January, the army proclaimed the "total liberation" of the eastern side of the city. The Iraqi forces is supported by a US-led coalition of western countries, Shia militias and Kurdish Peshmerga forces in its offensive to retake the city, launched more than four months ago.

Mosul fell under Isis control in 2014. the group's leader Abu Bakr al-Baghdadi declared the city "the crown jewel" of their so-called caliphate as it was the biggest one under their control.

Despite the liberation of the eastern side of the city, around 750,000 remain at risk, living under Isis control on the bank of the river. The UN fears that around of a third of them could be displaced by the conflict as the fighting moves to the densely-populated western Mosul and fears for the lives of those who remain, as nearly half of the casualties in the conflict so far have been civilians.

According to the UN Refugee Agency, as many as 190,000 people fled the city since the army offensive began on 17 October, but around 30,000 have now returned. An increasing amount of returnees are crowding the checkpoints at the border with the Kurdish territories.

The security forces are reportedly struggling to process all the requests, overwhelmed by the thousands of civilians hoping to return home as well as, hundreds of other people who are transporting aid and commercial goods into recently retaken territory.

Norman Mohammed, who fled the city three years ago, waited a whole day at the checkpoint in vain, as he was turned back by Kurdish security forces. "We want to see our families and they are useless. I went back to Irbil and I came back today, early morning," he told The Associated Press on 7 February. After waiting the whole day for a second time, the man was again sent back to Irbil.