United Nations, Jun 1 (IANS): Nearly 3,700 people, or 624 families, have fled Fallujah over the past week amid a new offensive by Iraqi forces to retake the besieged city from the Islamic State (IS), the UN said on Tuesday.

Meanwhile, humanitarian officials also reported that those civilians left behind risk being used as "human shields" by the terrorists, Xinhua reported.

According to figures provided by authorities, about 1,300 of them were staying in the al-Iraq camp in the Ameriyat al-Falluja district, where the Office of the UN High Commissioner for Refugees (UNHCR) was working to provide assistance.

Others were scattered in one of several other government-run camps in the district or staying with relatives.

Iraqi forces were helping to transport families escaping the city, and have set up a hotline to provide information to people wanting to leave, UN officials said.

The UNHCR has received reports of casualties among civilians in the Fallujah city centre due to heavy shelling, including seven members of one family on May 28.

The officials also noted that 500 men and boys over 12-years-old were held for security screening, which can take five to seven days, and some 27 men were released on Monday.

Meanwhile, the UN humanitarian coordinator for Iraq reported on Tuesday that around 50,000 civilians trapped inside the Iraqi city of Fallujah, risk being turned into "human shields" by the terrorist group also known as Da'esh.