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 officials said the militants captured Rutba, about 90 miles (150 kilometers) east of the Jordanian border, late Saturday. Residents were on Sunday negotiating with the militants to leave after an army unit on the town’s outskirts threatened to start shelling.
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.
In a reflection of the bitter divide, thousands of heavily armed Shiite militiamen — eager to take on the Sunni insurgents — marched through Iraqi cities in military-style parades Saturday on streets where many of them battled U.S. forces a half decade ago.
The towns of Qaim, Rawah, Anah and Rutba are the first seized in predominantly Sunni Anbar province since fighters from the Islamic State of Iraq and the Levant 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 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.
Rutba has a population of 40,000 but it has recently been home to 20,000 displaced from Fallujah and Ramadi.
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.
The Islamic State and allied militants have carved out a large fiefdom along the Iraqi-Syrian border. Control over crossings like that one in Qaim allows them to more easily move weapons and heavy equipment. Rebels control the Syrian side of the crossing.
Al-Maliki’s Shiite-dominated government has struggled to push back against the Sunni militants, who have seized large swaths of the country’s north since taking control of the second-largest city of Mosul on June 10 as troops melted away.
The prime minister, who has led the country since 2006 and has not yet secured a third term after continued…