KHAZER, Iraq – Some 30,000 people have returned to Mosul since Iraqi forces launched a massive operation in October to retake the country’s second largest city from the Islamic State group, the U.N. said Tuesday.

The number of returnees has increased since Iraqi forces drove the militants from the eastern half of the city last month, according to U.N. Office for the Coordination of Humanitarian Aid. IS still holds western Mosul, home to an estimated 750,000 people.

At times, the crowds have overwhelmed checkpoints outside the city, where security forces are screening those who want to return.

Norman Mohammed, who fled the city three years ago, said he had waited at the Khazer checkpoint all day Monday, hoping to enter, but was turned back by Kurdish security forces, who told him to return to the Kurdish regional capital, Irbil.

“We want to see our families and they are useless. I went back to Irbil and I came back today, early morning at 6 a.m.,” he said. After waiting at the checkpoint for a second day, he was again sent back.

Kurdish officials at the checkpoint said they could not process the thousands of civilians hoping to return home as well as hundreds of others ferrying aid and commercial goods into recently retaken territory.

IS militants captured Mosul in a matter of days in the summer of 2014, when they swept across northern and central Iraq. Since then, Iraqi forces have slowly clawed back territory, leaving western Mosul as the last major urban area held by IS in Iraq.

Some 190,000 people have been displaced in Iraq since 2014, either by the militants or military operations against them, according to the U.N.