Iraqi special forces launched an operation on one of Islamic State of Iraq and the Levant's (ISIL) most emblematic bastions, Fallujah, as the group counter-attacked in both Iraq and neighbouring Syria.
In January 2014, it became the first Iraqi city to fall to ISIL - also known as ISIS - and it subsequently overran wide areas of the north and west of Iraq, declaring a caliphate that included seized territory in Syria.
On Monday, army units advanced to the southern entrance to Fallujah, "steadily advancing" under air cover from the US-led coalition, according to a military statement read out on state TV. A Reuters TV crew at the scene said explosions and gunfire were ripping through Fallujah's southern Naimiya district.
The offensive is causing alarm among international aid organisations over the humanitarian situation in the city, where more than 50,000 civilians remain trapped with limited access to water, food and healthcare.
Fallujah is the second-largest Iraqi city under control of ISIL, after Mosul, the group's de facto capital in the north that had a pre-war population of about two million.