Fighters from the Islamic State group killed at least 18 members of two families as they attempted to flee the besieged jihadist bastion of Fallujah, relatives said on Sunday.
IS has been using civilians as human shields to defend its stronghold since Iraqi forces launched a vast offensive on May 22-23, on multiple occasions shooting those who tried to escape.
Civilians who reached the safety of displacement camps south of the city and several aid organisations have reported cases of residents being shot dead, mostly as they tried to cross the Euphrates River to reach Iraqi government forces.
In the worst known case so far, IS fighters killed at least 18 members of two families Friday as they attempted to flee, southeast of the city, relatives and a security officer told AFP by phone.
"A number of residents were trying to flee and as they neared the Al-Salam intersection, Daesh (IS) opened fire on them, killing 18 and wounding dozens," a senior officer at the Joint Operations Command told AFP.
The officer, speaking on condition of anonymity because he is not authorised to talk to the press, said the army was able to rescue some of the wounded.
Relatives said the initial group that tried to sneak out of IS-controlled areas on Friday included around 100 individuals, including a majority of women and children.
The group were all from the same two families -- Albu Hatem and Albu Saleh -- and had made a previous failed attempt to leave days earlier.
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"When they got near the intersection, which is the meeting point with the Iraqi forces, two gunmen on motorbikes arrived and sprayed them with gunfire," said Ahmed al-Ghneim, a relative.
Two of the survivors, relatives from the Albu Saleh family, are staying at his home in Amriyat al-Fallujah, south of Fallujah.
"Some of the residents jumped into the canal, some fled to a nearby house. When they entered it, it blew up on them because it was booby-trapped," he said.
"Some survivors were forced to go back inside Fallujah. Daesh took 17 of the wounded to Fallujah hospital," Ghneim said.
Sami Abu Hatem, a relative who was already living in a camp in Amriyat al-Fallujah, confirmed that version of events.
"Three of my direct relatives, a man with two young children, were among those massacred," he said.
Abu Hatem he said he knew of 18 members of the group being killed and added that more were feared missing after jumping in the nearby canal.
According to aid groups running displacements camps outside Fallujah, only small numbers of residents have managed to flee the city centre.
Most of the 24,000 people who have escaped IS rule since the start of the operation three weeks ago are from outlying rural areas.