Iraqi forces launched an assault yesterday to recapture the Old City, the last district of Mosul still held by the Islamic State group after a months-long offensive.
Commanders say the jihadists are putting up fierce resistance and there are concerns for the more than 100,000 civilians believed to remain inside the Old City.
Late yesterday, Iraqi forces dropped nearly 500,000 leaflets over the city, warning that they "have started attacking from all directions".
Iraqi forces have also stationed Humvees by the Grand Mosque on the eastern side of Mosul, which faces the Old City and is mounted with speakers.
More From This Section
The loudspeakers have been blaring messages to civilians, saying Iraqi forces "are about to end your suffering".
Messages were also being broadcast to IS fighters, telling them: "You have only this choice: surrender or die".
The push into Mosul's Old City -- a densely populated warren of narrow alleyways on the western side of Iraq's second city -- marks the culmination of a months-long campaign by Iraqi forces to retake IS's last major urban stronghold in the country.