MOSUL, Iraq — Half a dozen units of fighters for the militant group that calls itself the Islamic State were holed up in western Mosul earlier this week, beginning their morning radio checks at just after 4 a.m. It was still dark, and Iraqi forces deployed a few blocks away were listening in as they prepared an advance on the city’s al-Rifai neighborhood.

‘‘Thirty, what’s new? . . . 120, do you read me? What’s up?’’ the militant radio operator asked.

About 40 minutes later the first US-led coalition airstrike hit, as Iraqi forces pushed across a main road and began clearing the neighborhood’s narrow streets.

Over the next 12 hours, more than 10 coalition airstrikes hit al-Rifai’s eastern edge. Most targeted small teams of two or three fighters manning sniper rifles or machine guns so that Iraq’s special forces units could advance on the ground.

Military operations like the one in al-Rifai this week are accelerating in Mosul as part of a drive to retake the handful of districts still under Islamists control before the holy month of Ramadan begins at the end of May. And despite recent allegations of increased civilian casualties, advances on the ground continue to be backed by heavy airstrikes and artillery.

Launched in mid-February, the fight for Mosul’s western sector has been marked by some of the most difficult fighting and catastrophic destruction yet in Iraq’s war against the militants. The brutality of the operation was highlighted by a single incident just a month into the operation — a US airstrike on March 17 that killed more than 100 people sheltering in a home, according to residents and other witnesses interviewed.

Associated Press