BAGHDAD (AP) — An aid organization says a two-year-old boy has been killed while fleeing Fallujah with his family amid a government offensive to retake the Iraqi city from the Islamic State group.

The Norwegian Refugee Council, which works with refugees and internally displaced Iraqis, cited a relative on Thursday as saying that an IS fighter shot the boy as he was being carried out of the city by his mother on Monday.

It says the gunfire hit the mother's shoulder and killed her son. Another son and three daughters, all under eight years old, escaped unharmed.

There are not any official figures for how many civilians have been killed while fleeing Fallujah.

Aid groups estimate that 50,000 civilians remain trapped inside Fallujah, which has been under IS control for over two years.