BAGHDAD (AP) — Islamic State group militants launched an assault Thursday on a small town in western Iraq, a military spokesman said, as the United Nations warned that 10 months of violence in the country has taken a heavy toll on civilians.

Iraq is in its worst crisis since the 2011 withdrawal of U.S. troops as Sunni militant groups led by the al-Qaida breakaway Islamic State group have seized a third of the country since early this year. In one lightning offensive over the summer, Iraq’s U.S.-trained army and security forces melted away as the extremists advanced and captured key cities and towns in country’s north.