BAGHDAD - Sunni militants have seized another town in Iraq's western Anbar province, the fourth to fall in two days, officials said Sunday, in what is shaping up to be a major offensive in one of Iraq's most restive regions.
The latest advance has dealt another blow to Shiite Prime Minister Nouri al-Maliki, who is fighting for his political life even as forces beyond his control are pushing the country toward a sectarian showdown.
The militants captured Rutba, about 90 miles (150 kilometers) east of the Jordanian border, late Saturday, the officials said.
Residents were on Sunday negotiating with the militants to leave after an army unit on the town's outskirts threatened to start shelling.
The towns of Qaim, Rawah, Anah and Rutba are the first seized in the mainly Sunni Anbar province since fighters from the Islamic State of Iraq and the Levant and their allies overran the city of Fallujah and parts of the provincial capital of Ramadi earlier this year.
The capture of Rawah on the Euphrates River and the nearby town of Anah appeared to be part of a march toward a key dam in the city of Haditha, the destruction of which would damage the country's electrical grid and cause major flooding.
Taking Rutba gives the insurgents control over the final stretch of a major highway to neighboring Jordan, a key artery for passengers and goods that has been infrequently used for months because of deteriorating security.
Iraqi military officials said more than 2,000 troops were quickly dispatched to the site of the dam to protect it. They spoke on condition of anonymity because they were not authorized to speak to the media.
Chief military spokesman, Lt. Gen. Qassim al-Moussawi, acknowledged the fall of the Anbar towns, saying government forces had made a tactical retreat and planned to retake them. He provided no further details.