US-led campaign against DAESH has moved up a gear in recent weeks, while victory in Falluja has also lent fresh momentum to the campaign to recapture Mosul.
At least 250 suspected DAESH terrorists were killed and 40 vehicles destroyed in a series of air strikes carried out by the US-led coalition around the Iraqi city of Falluja on Wednesday, US officials have said.
The officials spoke on condition of anonymity to describe the operation and noted preliminary figures can change.
If the figures are confirmed, the strikes would be among the most deadly ever against DAESH and are just the latest battlefield setback suffered by the militant group.
The terrorist group has declared a self-proclaimed caliphate in large swathes of Syria and Iraq, naming the Syrian city of Raqqa as its capital.
The latest strikes follow Wednesday's triple suicide bombing and gun attack that killed at least 41 people at Istanbul's main airport.
Turkey blamed the attack on DAESH.
CIA chief John Brennan told a forum in Washington the attack bore the hallmarks of DAESH "depravity".
He acknowledged there was a long road ahead battling the group, particularly its ability to incite attacks.
"We've made, I think, some significant progress, along with our coalition partners, in Syria and Iraq, where most of the DAESH members are resident right now," Brennan said.
"But DAESH's ability to continue to propagate its narrative, as well as to incite and carry out these attacks — I think we still have a ways to go before we're able to say that we have made some significant progress against them," he added.
Iraqi forces press towards key air base south of Mosul
On the battlefield, the US-led campaign against DAESH has moved up a gear in recent weeks, with the Iraqi government declaring victory over the militant group in Falluja.
Iraq's military said it advanced through northern villages held by the militant group on Wednesday, on its way to an airfield which could serve as the staging ground for a future offensive on Mosul,
Mosul is Iraq's largest northern city and the biggest anywhere within DAESH control.
Iraqi Prime Minister Haider al-Abadi has pledged to retake Mosul this year.
Army and counter-terrorism forces recaptured Telol al-Baj, about 260 km north of Baghdad on the main north-south road on Tuesday, a senior commander participating in the offensive told Reuters.
US-led coalition air strikes have helped repel suicide car bomb attacks, the commander said.
Both sides have suffered casualties, but most militants have fled into the desert, he added.
The troops are now around 45 km from the airbase at Qayara, less than two weeks after they set out from the refinery town of Baiji, military officials said.
Retaking another refinery near Qayara with a production capacity of 16,000 barrels per day could also hit DAESH's finances.
Iraqi forces also shelled DAESH positions in Haj Ali on Wednesday in preparation for a ground advance that would allow them to reach the river bank, an army source said.
The offensives have so far displaced thousands of civilians from their homes, and the United Nations expects several thousand more to flee in coming days.
Upcoming military offensives in Iraq against DAESH, including an assault on Mosul, could displace at least 2.3 million people, a UN official said last week.
An alliance of militias have also launched a major offensive against the militant group in the city of Manbij in northern Syria.
Still, in a reminder of the back-and-forth nature of the war, US-backed Syrian rebels were pushed back from the outskirts of a DAESH-held town on the border with Iraq.