WASHINGTON - Following the Islamic State group’s bloody weekend seizure of much of the Iraqi city of Ramadi, the U.S.-led coalition has increased airstrikes and Shi’ite paramility units are preparing to deploy to the predominantly Sunni city.

Hundreds of people reportedly were killed as the militants flooded into the capital city of Anbar province, overpowering Iraqi troops.

US-Led Coalition Steps Up Airstrikes in Ramadi

"We estimate that 500 people have been killed, both civilians and military, and approximately 8,000 have fled the city,'' the Associated Press quoted Anbar spokesman Muhannad Haimour as saying.

US-Led Coalition Steps Up Airstrikes in Ramadi

The figures could not be independently confirmed, but IS militants previously have slaughtered hundreds of soldiers and civilians following major victories. Reuters news agency was reporting at least 6,000 people have left Ramadi in the past few days.

US-Led Coalition Steps Up Airstrikes in Ramadi

U.S. Secretary of State John Kerry voiced optimism that IS militants would lose their grip on the city.

"I am convinced that as the forces are redeployed, and as the days flow in the weeks ahead, that's going to change, as overall [they] have been driven back," Kerry said at a news conference in Seoul, South Korea, where he was meeting with government leaders. "... I am absolutely confident in the days ahead that will be reversed."

The coalition conducted 19 strikes in and around Ramadi over the past 72 hours, a coalition spokesman said, according to the AP. The action came at the request of Iraqi security forces.

Iraq's prime minister, Haider al-Abadi, approved the Shi'ite militia's deployment to Ramadi. He earlier had opposed it because of intense sectarian divisions.

The U.S. Defense Department is challenging the Islamic State group’s claim that it has seized Ramadi. A Pentagon spokesman said that the situation on the ground is unclear and that the U.S.-led coalition is supporting the Iraqis with airpower.

On Sunday, Combined Joint Task Force Operation Inherent Resolve conducted seven airstrikes that targeted several IS tactical units, destroying four resupply structures, three fighting positions, two insurgent-held buildings, two heavy machine guns and two vehicles. Airstrikes also were conducted against IS targets near Bayji, Fallujah, Mosul, Sinjar and Tal Afar.

The IS group fought its way to Ramadi’s center Friday. The final push by militants began Sunday with bombings that killed at least 10 Iraqi security force personnel. Prime Minister Haidar al-Abadi urged Iraqi forces not to abandon their posts and ordered Shi’ite militia to prepare to enter the fight for Anbar province.

Rick Brennan, a RAND Corp. senior political scientist and career U.S. Army officer, said Iraqi security forces still held pockets of the city.

“It’s contested," he said of the IS group's claim of control. "It was significant in that they captured the Anbar Operations Center and they were able to raise the [IS] flag. But, they no sooner got there then they had to disperse and go out into other areas out of fear of U.S. airstrikes. So, yes, it was a tactical victory for ISIS, but the battle is still taking place."

Brennan said that despite Iraqi-led forces' retaking of the city of Tikrit in early April, IS remains in control of Fallujah and Hit in the west, as well as part of the oil refinery near Bayji and Mosul to the north. The Pentagon had said in April that, since the U.S.-led air campaign began last August, the IS group had lost between 25 and 30 percent of the Iraqi territory it controlled.

In Syria, troops have pushed IS fighters back from the ancient city of Palmyra, a U.N.-designated World Heritage site, in a battle that reportedly left hundreds dead.

U.S. lawmakers praised U.S. Special Forces for a raid in eastern Syria late Friday into Saturday that killed senior IS leader Abu Sayyaf and resulted in the capture of his wife, Umm Sayyaf - a suspected IS member who likely played a role in the group’s terrorist activities. House Intelligence chairman Congressman Devin Nunes said on CBS’s it is a tactic he and others had long advocated as a way to gather intelligence.

"It takes guts for the [Obama] administration and our military to put an action like this together. It was successful. We’re happy they got back and got back safely. Now, over the coming weeks, we’ll know what they were able to gather there," said Nunes.

Nunes describes the U.S. strategy against the IS group as one of containment that will not degrade or destroy it because the militant group extends beyond Iraq and Syria into North Africa.