A CNN crew watching from Kurdish positions on Mount Zartak, to the southeast of Mosul, saw at least 12 blasts in the city and heard jets streaking overhead.
ISIS swept into Mosul in June, with Iraqi forces at the time largely fleeing the advance. The Sunni Muslim terror group, also called the Islamic State in Iraq and Syria, folded Mosul into what it calls its Islamic caliphate -- territory that it has captured in both countries.
Kurdish forces, which protect a Kurdish autonomous region in northern Iraq, recently have been trying to surround Mosul to cut off ISIS's lines of supply from Syria, setting up what could be an eventual assault to try to expel the terror group from the city.
Kurdish forces say the frequency and intensity of airstrikes on Mosul have increased sharply since Tuesday, when ISIS released a video showing its fighters burning to death a Jordanian captive pilot, Lt. Moath al-Kasasbeh, who was captured in December after his jet crashed in Syria.
Airstrikes also hit ISIS targets near the terror group's de facto capital of Raqqa, Syria, on Saturday, anti-ISIS activists there said.
At least 10 explosions were reported Saturday in Hazema, north of Raqqa, and six other strikes happened in Tabqa to the west, the activist group "Raqqa is Being Slaughtered Silently" said on Twitter.
Jordan, one of Syria's southern neighbors, again sent its jets to strike ISIS targets Saturday, and all of the jets returned safely to their bases, Jordanian state-run TV reported. Jordan, which has promised revenge for al-Kasasbeh, has publicly pressed to participate in more of the coalition's airstrikes against ISIS in Syria.
U.S. and coalition aircraft conducted 11 airstrikes over Syria and 15 airstrikes over Iraq from 8 a.m. Friday to 8 a.m. Saturday, the U.S. military said.
ISIS declared it had established a caliphate spanning Iraq and Syria last year. Since then, it has gone on a murderous rampage that has included beheadings of foreigners. Hundreds of thousands of Iraqis and Syrians have fled areas it has seized.
The United States, along with European and Arab nations, began airstrikes against the terror group last year.
Kurds say ISIS destroyed key Iraq bridge
ISIS militants have destroyed a bridge they recently used to assault Iraq's oil-rich Kirkuk city -- a possible attempt to hinder a counterattack against them, a Kurdish political and military leader said Saturday.
About 30 kilometers southwest of Kirkuk, ISIS late Friday blew up a bridge that helps connect an ISIS-held area to the city, said Saman Jabari, a senior Kurdish political leader who also commands Kurdish Peshmerga troops near Kirkuk.
ISIS had used the bridge to reach the Kirkuk area in a surprise attack on January 30, Jabari said. Kurdish troops have counter-attacked since.
Suicide bombings kill dozens in Baghdad
As the coalition's struggle against ISIS continued in northern Iraq, a pair of suicide bombings on Saturday killed at least three dozen people hundreds of kilometers to the south in Iraq's capital, Baghdad, a police source in the city said.
An attacker blew himself up at a busy restaurant in southeastern Baghdad's Al-Jadida neighborhood, killing at least 30 people and injuring 66 others, the police source said.
In the center of the city, a different suicide bombing at a market killed six people and injured 28 others, the source said.
Information about who was responsible for the bombings wasn't immediately available.