MOSUL, Iraq — Heavy fighting erupted in the eastern neighborhoods of Mosul on Friday as Iraqi special forces launched an assault deeper into the urban areas of the city and swung round to attack Islamic State militants from a second entry point, to the northeast.

Columns of armored vehicles wound through open desert to open the new front, pushing through dirt berms, drawing heavy fire and calling in airstrikes to enter the middle class neighborhoods of Tahrir and Zahara.