Supported by the US-led anti-IS coalition, Iraqi government forces and a Kurdish-Arab alliance in Syria are battling to push the jihadists from Mosul and Raqa, the last two major urban centres under their control.
Intense fighting since last week has forced tens of thousands of people from their homes, raising fears for many more civilians still trapped in areas of IS's so-called "caliphate".
In Iraq, security forces retook a series of government buildings that were one of the targets of a renewed push in west Mosul launched yesterday, the Joint Operations Command said.
And the Counter-Terrorism Service, the country's premier special forces unit, retook Al-Sumood neighbourhood, another target in the drive, and attacked Al-Mansur, according to the JOC.
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The operation to retake west Mosul was launched on February 19, but had slowed due to several days of bad weather until a fresh push began yesterday.
AFP reporters in west Mosul witnessed intense clashes, with heavy automatic weapons fire and clouds of black smoke billowing over the city.
Mosul is divided by the Tigris River, and while the series of bridges crossing it have either been damaged or destroyed, they would provide a link between the government-held east and IS-held west Mosul if they can be repaired or otherwise bridged.
Iraqi forces recaptured the western side of the fourth bridge, which is south of Al-Hurriyah, at the end of February.
The fighting in west Mosul has sparked an exodus from that side of the city, pushing more than 50,000 people to flee, the International Organization for Migration said.
In Syria, US-backed forces today cut off a key supply route between IS stronghold Raqa and the group's territory in Deir Ezzor province.
The Syrian Democratic Forces (SDF), an alliance of Kurdish and Arab fighters, seized control of the only major road linking Raqa along the Euphrates valley to Deir Ezzor, the Syrian Observatory for Human Rights monitoring group said.
"The route... Linking Raqa to Deir Ezzor was cut this morning," an SDF commander confirmed.