Islamic State (ISIS/ISIL) jihadists are using “several hundred families” in Fallujah as “human shields” as they engage in bloody battles with Iraqi troops, backed by the United States and Iran-allied Shiite militias, for control over the strategic city, reports the United Nations Refugee Agency.

“UNCHR has received reports of casualties among civilians in Falluja city centre due to heavy shelling, including seven members of one family on May 28,” William Spindler, a spokesperson for the agency officially known as the United Nations High Commissioner for Refugees (UNHCR), told reporters at the UN headquarters in Geneva on Tuesday. “There are also reports of several hundred families being used as human shields by ISIL in the centre of Falluja.”

Up to an estimated 50,000 civilians remain trapped in Fallujah, prevented from fleeing by terrorists as the city continues to be heavily bombarded by the Iraqi military, notes UNHCR in a press release.

The UN agency notes:

Conditions for those trapped in the city are dire. UNHCR previously noted reports of several starvation-related deaths amid food shortages. Families have had to rely on unsafe water sources, including drainage water from irrigation canals. Health facilities and medications are unavailable…

Inside Falluja, there have been reports of a dramatic increase in the number of executions of men and older boys for refusing to fight on behalf of ISIL. Other reports say a number of people attempting to leave have been executed or whipped, and one man’s leg was reportedly amputated. In addition, many people are reported to have been killed or buried alive under the rubble of their homes in the course of ongoing military operations.

U.S.-backed Iraqi troops and Shiite militias linked to Iran launched an operation last week to root the jihadist group out of Fallujah, considered one of two remaining strongholds controlled by the Islamic State, the other being Mosul, Iraq’s second largest city.

On Tuesday, ISIS terrorists repelled an Iraqi army assault on the city of Fallujah with a counter-attack, Reuters reports, adding, “A week after Baghdad announced the start of the assault, its troops advanced in large numbers into the city limits for the first time on Monday, pouring into rural territory on its southern outskirts but stopping short of the main built-up area.”

“Iraqi forces have been sealing off Fallujah for months and those still in city — IS fighters and civilians alike — have nowhere to go,” reports Agence France-Presse (AFP).

However, UNHCR points out that the Iraqi military is helping their fellow citizens escape the besieged city, located nearly 35 miles west of Baghdad in Anbar, Iraq’s largest province.

Male residents seeking to leave the city are subjected to security screenings.

“UNHCR understands approximately 500 men and boys over 12-years-old are held for security screening which can take five to seven days. People are being released after this process, and we understand some 27 men were released yesterday (Monday 30 May),” said Spindler.

Since the Iraqi military launched the new offensive to recapture Falluja from ISIS, about 3,700 Iraqis (624 families) have managed to flee from the city, he revealed, citing figures provided by local authorities.

The al-Iraq camp in Anbar’s Amiriyat al-Falluja district is reportedly housing about 1,300 of the escapees.

Some Fallujah residents can also be found in Iraqi government-run camps across the district or are with family members, according to UNHCR.

In the past, people have been prevented from leaving the city.

Fallujah, described by AFP as “an emblematic bastion” for ISIS, became the first major city to fall under the jihadist group’s control.

AFP reports that the Iraqi government lost control of the city “months” prior to ISIS seizing large swathes of Iraq in June 2014.

The UN agency notes:

UNHCR and its partner, Muslim Aid, are distributing emergency relief items to families who have escaped the city and are sheltering at [the camp in] Amiriyat al-Falluja. The agency will also open two new camps in coming days in Habbaniyah Tourist City, that will able to accommodate 500 newly displaced families…

For the past few weeks, there has been intensified fighting around Falluja and airstrikes by coalition forces as the Iraqi Security Forces advanced towards the city. Families that escaped have told UNHCR and its protection partners harrowing tales of their flight, trekking for hours at night, moving across fields and hiding in disused irrigation pipes. Others have lost their lives trying to leave the city, including women and children.

Falluja reportedly had a pre-war population of 2 million.