Islamic State militants in Iraq took partial control of a water dam and military barracks guarding it in the western Anbar province after fierce fighting through the night that continued on Saturday, security sources and witnesses said.
Three suicide car bombs also exploded at a border crossing between Iraq and Jordan on Saturday, killing four soldiers, a witness and an Iraqi border police source said, in an attack claimed shortly afterwards by Islamic State.
The Islamic State militant group claimed responsibility for the attack in a video, saying it had targeted a government complex, control point for the border crossing, and army patrol, according to monitoring group SITE.
A Jordanian official said his government had responded by stepping up security measures at the Tureibil crossing, while an Iraqi defense ministry spokesman said Baghdad would investigate the assault.
The Iraqi government announced a new offensive this month to recapture parts of Anbar, Iraq's Sunni Muslim heartland, from Islamic State, in an attempt to build on an earlier victory against the group in the central city of Tikrit.
But the hardline Sunni militants struck back by attacking Ramadi, the provincial capital of Anbar, prompting thousands of families to flee. They also hit Baiji, Iraq's largest refinery last week.
Late on Friday, the insurgents attacked the security perimeter at al-Thirthar dam with explosive-laden vehicles and then battled army forces in clashes that continued on Saturday, police and army sources told Reuters.
Dozens of Iraqi troops were killed in the fighting, but poor communications in the area made it difficult to confirm a precise figure, said Athal al-Fahdawi, an Anbar provincial council member. Army sources said two senior officers were among the dead.
Officials from Iraq's defense and interior ministries could not immediately be reached for comment.
Security forces and Shi'ite paramilitaries have regained some ground in Iraq since Islamic State proclaimed a caliphate straddling the border of Syria and Iraq, but core Sunni territories such as Anbar remain under Islamic State control.
A video posted online on Saturday by Islamic State's official media organization appeared to show its fighters moving about freely at al-Thirthar dam, which serves as a flood control for Baghdad and other cities.
A black flag commonly used by the militants is seen flying from a radio tower. Two bodies apparently belonging to Iraqi forces also appear in the footage.
(Reporting by Baghdad newsroom, Suleiman al-Khalidi in Amman, Sami Aboudi in Dubai; Editing by Raissa Kasolowsky)