Militants from the so-called Islamic State have launched a dawn counter-attack as Iraqi government troops push into the city of Falluja.
A day after troops advanced through the southern suburb of Nuaimiya, scores of IS fighters attacked them, army officers told news agencies.
The army defeated the attackers but suffered casualties, the sources said.
Aid workers are increasingly concerned for the safety of 50,000 civilians said to be trapped in Falluja.
Reports speak of people starving to death and of being killed for refusing to fight for IS.
The Iraqi military has urged those remaining to either leave the city or stay indoors but IS is preventing civilians from fleeing.
Falluja fell to IS in January 2014, a key moment in the Sunni Muslim jihadist group’s rise that saw it declare a caliphate across swathes of Iraq and Syria.
It is one of two major cities held by IS in Iraq – the other being Mosul.