The United Nations has significantly revised the number of civilians believed to still be inside the besieged Iraqi town of Fallujah, a stronghold of the Islamic State of Iraq and the Levant (ISIL, or ISIS), to up to 90,000 - compared with a previous estimate of 50,000.
The offensive by the Iraqi army, backed by Shia militias, to dislodge ISIL from Fallujah began on May 23, but the city has been under a de facto siege for about six months.
In a telephone interview with the Reuters news agency in Baghdad, UN Humanitarian Coordinator for Iraq Lise Grande said on Wednesday that civilians could face a "harrowing" situation in the city 50km west of the Iraqi capital.
"We have underestimated how many civilians are in Fallujah," Grande said.
"People who are coming out are giving us the strong impression that we could be talking about maybe 80,000 to 90,000 civilians that are inside."
Thousands of civilians are caught in the crossfire in and around Fallujah, close to the capital Baghdad, as government forces and allied militias are trying to recapture the city.
READ MORE: Will Fallujah put an end to ISIL in Iraq?
Grande said that more than 20,000 people have managed to flee the city in extremely difficult conditions, having walked for days and faced ISIL fire to reach government-held areas.
"A number of them unfortunately didn't make it. We know that more than 10 people have drowned when they tried to cross the river," she said, also reporting cases where families lost their children while fleeing.
People fleeing Fallujah have been using anything that floats to help them get across the Euphrates, which is about 250 to 300 metres wide at the crossing point in farmland just south of the city.
The UN's upward revision came a day after an international aid group told Al Jazeera that civilians fleeing the city of Fallujah had been shot at by ISIL fighters holed up in the besieged city.
Nasr Muflahi, country director of the Norwegian Refugee Council, confirmed several such incidents based on testimonies from civilians who were directly targeted by ISIL gunmen on Sunday.
Also on Tuesday, the UN human rights chief said there were "extremely distressing, credible reports" that Iraqis fleeing the fighting in Fallujah were facing extreme abuse, and even death, at the hands of Shia armed groups allied with the government troops.
Zeid Ra'ad al-Hussein, citing witness testimonies, said on Tuesday that allegations of abuse included reports of multiple executions of men and boys, who were trying to escape the ISIL-held city.
"Eyewitnesses have described how armed groups operating in support of the Iraqi security forces are detaining the males for 'security screening'," Zeid said.
"[This] in some cases degenerates into physical violations and other forms of abuse, apparently in order to elicit forced confessions."
Source: Reuters And Al Jazeera