CAIRO — Islamic State militants staged attacks near Baghdad and the Libyan city of Surt on Tuesday, underscoring the group’s persistent strength on both fronts despite a monthslong American-led air campaign against it in Syria and Iraq.
In Libya, the Islamic State captured a critical power plant along the coastal road westward from its stronghold in Surt toward Misurata, a commercial center whose powerful militias are the backbone of a coalition that controls the capital, Tripoli. The loss was the second significant retreat in less than two weeks by the Misuratan militia, which the provisional government in Tripoli had originally sent to expel the Islamic State from Surt.
In Iraq, two gunmen wearing suicide vests attacked a local council building in Amariya al Falluja, a bold incursion into the center of a city about 37 miles southwest of Baghdad. The city is one of the last bastions of government control in Anbar Province after Islamic State militants captured the major city of Ramadi three weeks ago, and Iraqi troops have been battling against the militants on the outskirts of Amariya al Falluja for months.
The extremist group, also known as ISIS or ISIL, is still gaining ground in both countries by filling vacuums created by political deadlock. In Iraq, the Shiite-dominated government in Baghdad has failed to provide convincing evidence of its commitment to equal justice for members of the Sunni minority, spurring sympathy for the Sunni extremists of the Islamic State, while years of corruption and nepotism have hollowed out the armed forces.
In Libya, two competing militia factions — each with its own government — remain so preoccupied by their conflict that they are putting up little resistance to the Islamic State’s advances. Neither faction has provided an alternative model of effective or responsive governance.
In both countries, the United States and other Western powers are struggling to find effective partners to help engage the Islamic State, or even contain it.
In Libya, the capture of the power plant means the Islamic State can threaten to cut off electricity to parts of the central and western regions of the country.
Less than two weeks have passed since the group’s last big advance: It captured the badly damaged airport on the outskirts of Surt and a water utility plant that the Misuratan militia had been using as a base.
Leaders of the militia had said at the time of that retreat that they were pulling back to the power plant on the road toward Misurata in order to defend it after other fighters there had pulled out, complaining that they had not been paid.
In a statement posed on Facebook on Tuesday, the militia — known as Brigade 166 — said that it had been forced to retreat again after losing five fighters in an early morning attack by the Islamic State militants, and it blamed the Tripoli government.
“Up until now, the 166 brigade has not received any support from the general staff of the army,” the statement said, referring to the “army” of the provisional government in Tripoli.
The Tripoli government “will have to dispatch a force as soon as possible,” the statement continued. “Until then we are going to be powerless.”
The Misurata-dominated provisional government in Tripoli is locked in a power struggle with a rival military leader, Gen. Khalifa Hifter; he has the backing of the internationally recognized government, based in the eastern cities of Tobruk and Bayda.
While the factions have battled each other, extremists pledging allegiance to the Islamic State have established a growing presence on the Libyan shores of the Mediterranean even as they have come under attack in Syria and Iraq. A faction of the Islamist fighters in the eastern city of Darnah has pledged allegiance to the group, and so has a group in the southern desert region.
A third unit of Islamic State fighters has captured Surt, the hometown and birthplace of Col. Muammar el-Qaddafi, and it has become the Islamic State’s most significant Libyan foothold. The group has established full control of the center of the city since at least the beginning of the year, and militants acting in the name of the Islamic State have staged attacks on Misurata forces, as well as a mass shooting at a luxury hotel in Tripoli and less lethal attacks on embassies and government buildings.
United Nations diplomats have been working for six months to negotiate the formation of a unity government that would bring together Libya’s two rival factions, in part to more effectively counter the Islamic State’s expansion.
The diplomats leading the effort released what they called a final draft of a unity proposal late Monday night. On Tuesday, representatives of both sides who had helped negotiate the deal traveled to Berlin to present it to the five permanent members of the United Nations Security Council, diplomats with them said. The Security Council is expected to provide support for the proposed unity government as it attempts to stabilize the country.
Western diplomats hope that the deal will bring together moderates from both sides to fight against hard-liners in each camp, as well as the Islamic State. But it was not clear on Tuesday how much support or opposition the final proposal might win within the two warring factions.
In Iraq, the attack on the council building in Amariya al Falluja on Tuesday underscored the Islamic State’s sustained ability to strike even inside tightly controlled government territory.
Two Islamic State gunmen wearing police uniforms and suicide vests opened fire during a meeting of local sheikhs, according to Shaker al-Issawi, the head of the council. The gunmen killed two civilians and two police officers before Mr. Issawi’s bodyguards shot and killed the attackers, Mr. Issawi said.
Mr. Issawi added that the authorities believed that the gunmen had been hiding among the thousands of displaced Sunni Muslims from Anbar Province who had been sheltering in Amariya al Falluja.
Mr. Issawi’s assertion that displaced Sunnis were responsible threatened to further inflame local sectarian tensions.