Militants seized part of the Iraqi town of Dhuluiyah and bombed government buildings and a bridge on Sunday as they pressed a renewed offensive for a third day.
Six people, including four police, were killed in the fighting for the town, which the militants took in a lightning advance last month before its recapture by police and local residents, district official Marwan Mitaab said.
The assault on the town, just 80 kilometres (50 miles) north of Baghdad, began early on Sunday and has since overrun more than half of it, Mitaab said.
In what appeared to be an attempt to stop reinforcements reaching a major military base to the southwest, the militants blew up a bridge leading towards the nearby town of Balad, said a police colonel, who confirmed the death toll given by Mitaab.
The officer said the militants also bombed three police stations, the local council headquarters and a court.
After a period in which battle lines have been relatively stagnant, jihadist-led militants seem to be making a renewed push to gain ground, after overrunning a vast swathe of territory north and west of Baghdad in their offensive that began in second city Mosul on June 9.
Security forces held off major attacks near Anbar provincial capital Ramadi and the strategic Euphrates valley town of Haditha on Friday and Saturday.
But Sunni Arab militants were able to overrun two towns in Diyala, northeast of Baghdad, on Saturday, despite a security force operation aimed at regaining territory in the confessionally mixed province.
The violence comes with Iraq's fractious parliament due to meet Sunday under heavy pressure to set differences aside and make progress on forming a new government to help counter the militant drive towards Baghdad.