Islamic State fighters on Friday seized control of key parts of Ramadi, the capital of Iraq’s largest province, in what appeared to be a significant blow to a U.S.-backed military campaign to retake territory from the insurgents.

The offensive began Thursday evening when ­Islamic State militants slipped into downtown Ramadi dressed in police uniforms, according to a militiaman fighting with the city police. The attackers opened fire on police officers, launching an assault that grew to involve rocket-propelled grenades, artillery and car bombs, he said. By Friday afternoon, the militants had hoisted the Islamic State’s black flag over the provincial government compound and had surrounded an important military operations hub in the west of the city, residents said.

The heavy fighting touched off panicked attempts by civilians to escape Ramadi.

“It was just like scenes of carnage in a World War II movie, with bombing all around and dead people in the streets,” said Ali Dulaimi, a 28-year-old student at Anbar University who fled central Ramadi with his three brothers and his parents.

“There were dead people lying all over the street as we ran away,” he said.

If the Islamic State takes control of Ramadi, it would gain a foothold less than 70 miles west of Baghdad. The city’s fall would be a serious setback for Iraq’s government, which only last month announced a campaign to push the Islamic State out of Anbar province.

Prime minister: A ‘setback’

While local officials and residents described a harrowing scene in Ramadi, the Iraqi government played down the significance of the fight. In a televised address Friday night, Prime Minister Haider al-Abadi referred to the attack on Ramadi as a “setback that happens, like in any battle.”

U.S. officials also said Iraqi forces hadn’t been defeated.

Brig. Gen. Thomas Weidley, chief of staff for the U.S.-led coalition battling the Islamic State, told reporters in Washington that the group’s fighters had executed a “complex attack” on Iraqi security forces in Ramadi. He said that the Iraqi forces were able to repel “most of these attacks” but that the militants had made gains. U.S. forces carried out “numerous airstrikes” Friday in Ramadi, according to State Department spokesman Jeff Rathke.

Weidley said the Islamic State was losing the overall fight in Iraq and Syria.

“We will see episodic temporary successes. But again, these typically don’t materialize into long-term gains,” he said.

But the governor of Anbar described the situation in Ramadi as “dire,” and local officials appealed for help. The militants mounted the operation in the city despite having been pounded for seven months by U.S. airstrikes in Anbar, showing their continued determination to gain territory.

“It’s desperate now,” said Omar Shehan, a tribal militiaman who fights alongside Ramadi police.

The Islamic State took control of key parts of Anbar in January 2014, including the city of Fallujah and some neighborhoods of Ramadi, and pushed farther into the province in June. But Iraq’s government held on to pockets of authority, including roughly 80 percent of Ramadi, a city of about 900,000 people, despite constant attacks.

A senior Ramadi police official, Maj. Omar Khamis al-Dahl, said by telephone that Islamic State fighters had made key gains Friday and that at least 60­ police officers had been killed.

“The city’s fallen. They’ve taken it,” Dahl said.

The governor of Anbar province, Sohaib Alrawi, said in a Twitter message that the situation in the city was “dire” but that battles were ongoing.

Dozens of soldiers fled the city overnight Thursday during the initial stages of the Islamic State attack, which involved heavy artillery and multiple car bombings, Dahl said. He said hundreds of police and soldiers in the provincial military headquarters were surrounded by the attackers.

“We have not received reinforcements from the government,” Dahl said, adding that he feared “a massacre.”

The attack on Ramadi comes more than a month after pro-
government forces, backed by U.S. airstrikes, drove Islamic State militants out of the city of Tikrit, an advance that officials in Baghdad touted as a major ­victory.

The Islamic State said in communiques Friday that it had used British, Syrian and Tunisian suicide bombers in its “invasion” of Ramadi, according to a translation by the SITE Intelligence Group. The militant group said it had killed and captured many “apostates” in an army barrack and at a police station it blew up.

The national government has not sent reinforcements to Ramadi because there is no place it can afford to spare troops, said ­Muhannad Haimour, spokesman for the Anbar governor, who is based in Baghdad.

“There are many fronts that the Iraqi army is dealing with,” he said, adding that resources were stretched thin. “But we believe that with the help of the international coalition, the situation will improve in the next few days.”

Iraq’s military capacity has been limited by the weakness of the army, which suffered large-scale defections last year and has been plagued by poor coordination and corruption, analysts say. Abadi’s government has been forced to rely on Iranian-backed Shiite militias to retake territory from the militants.

Appeared to be policemen

The Islamic State assault began Thursday evening with militants entering downtown Ramadi wearing uniforms, said Shehan, the tribal fighter.

“When they came to the front line last night, at first we thought they were policemen,” Shehan said, speaking by telephone from Ramadi. “Then they started killing us.”

The downtown compound that houses the Anbar provincial government fell about 2 p.m., according to police and residents. The nearby police headquarters also was damaged in the fighting, although officers had largely vacated the facility hours earlier, they said.

Anbar province has played a central role in Iraq’s conflicts since the toppling of Saddam Hussein, whose regime favored the Sunni tribes in the region.

Anbar became a center of the Sunni insurgency after the U.S.-led invasion and was the scene of some of the war’s most intense urban combat for American forces. In 2006, Anbar became a centerpiece of Washington’s counterinsurgency strategy when some main Sunni tribes made alliances of convenience with the U.S. military.

Missy Ryan and Brian Murphy
in Washington contributed to
this report.

Thousands of Iraqis flee as Islamic State makes gains in Anbar

Islamic State fighters are threatening to overrun Anbar province

Video: Families caught in the middle of Ramadi showdown