(CNN) The months-long fight for the key central Iraqi city of Ramadi now appears to be going ISIS 's way, with the Islamist extremist group capturing police headquarters, the Ramadi Great Mosque and even raising its trademark black flag over the provincial government building, sources said.

The ISIS push began Thursday, with armored bulldozers and at least 10 suicide bombings used to burst through gates and blast through walls in Ramadi, according to a security source who has since left the city. Dozens of militants followed them into the city center.

Anbar Gov. Suhaib Al-Rawi said the offensive, including suicide-attacks with explosive-rigged cars near security posts, continued into Friday.

Iraqi and allied forces fought back, with state-run Al-Iraqiya TV reporting at least eight coalition airstrikes on ISIS positions and Iraqi helicopters active in support of ground troops.

At least 47 Iraqi security forces and 26 civilians were killed in the fighting on Friday, according to two security sources.

Offering Washington's take on what's happening, a U.S. official said Ramadi "remains very fluid." The official characterized the situation as "50/50," with Iraqi forces in control of much of the city center and ISIS in the suburbs surrounding it.

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The White House said in a statement that the weapons include AT-4 shoulder-held rockets to counter vehicle-borne improvised explosive devices, as well as ammunition and other supplies.

This is in addition to airstrikes and other military support provided to Iraq by the United States.

"There will be good days and bad days in Iraq," State Department acting deputy spokesman Jeff Rathke said. ISIS "is trying to make today a bad day in Ramadi."

He added: "We continue to provide targeted air support in ISIL-held and contested areas, and that includes numerous airstrikes in Ramadi today."

The violence marks the latest in the tug-of-war for Ramadi. That city is just a few miles from an Iraqi army headquarters that ISIS blew up in March, and it's also just 70 miles (113 kilometers) west of Baghdad and in the middle of Iraq's Sunni Muslim heartland.

Each side has since alternated gains and losses in territory. Ramadi citizens have suffered greatly in the process. About 114,000 people have fled the area -- many heading to Baghdad -- in the last month alone, the United Nations refugee agency has said, citing the Iraqi government.

ISIS releases message from al-Baghdadi calling for recruits

Thursday's Ramadi offensive began on the same day that ISIS released an online audio statement in which ISIS leader Abu Bakr al-Baghdadi called for recruits from around the world to "fight in his land or wherever that may be."

CNN Arabic speakers said the voice was consistent with al-Baghdadi's previous recordings and showed no signs of frailty.

Al-Baghdadi mentions the Saudi air campaign in Yemen, which started March 26. The recording seems to prove he survived after reportedly being seriously wounded in a coalition airstrike in northern Iraq earlier this year.

Buck Sexton, a former CIA counterterrorism analyst, told CNN's Brooke Baldwin on Thursday that ISIS may be sending a message to its enemies.

"This is obviously ISIS trying to say, 'Yeah, yeah, you thought you got him but you didn't. Keep dreaming,' " he said.

UNESCO site among many under threat

The ISIS threat has spread through the region. Whether soldiers in places like Ramadi or individuals who lash out elsewhere in the name of ISIS, the Islamic extremist group has proven itself capable of tremendous violence and barbarity.

That includes putting pressure on Iraqi troops elsewhere in the Middle Eastern nation, like the soldiers who withdrew from a cement factory that was being used as a military base east of the Anbar city of Falluja.

ISIS also remains a force in Syria, where it is chief among the opposition groups fighting to unseat long embattled President Bashar al-Assad.

The carnage and harsh consequences of this fighting have been felt most everywhere, upsetting the lives of millions and threatening cultural sites that have stood for centuries. It's also opened the door to lawlessness, chaos and violence, whether perpetrated by ISIS or not.

Palmyra, a UNESCO World Heritage Site in the Homs countryside northeast of Damascus, is one of those places that has seen considerable bombing, firefights and other destruction in recent days.

Between the first and second century A.D., Palmyra "stood at the crossroads of several civilizations" -- specifically those of Greece, Rome and Persia -- according to UNESCO . Its grand streets, centuries-old temples and architectural flourishes make it "one of the most important cultural centers of the ancient world."

But now it is in danger.

Clashes between Syrian forces and ISIS militants on the outskirts of Palmyra left at least 15 Syrian fighters dead Friday, according to the London-based Syrian Observatory for Human Rights.

The SOHR also claims 23 family members of Syrian government workers were executed by ISIS in Amariya, which is near Palmyra.

"The site has already suffered four years of conflict. It suffered from looting and represents an irreplaceable treasure for the Syrian people and for the world," UNESCO Director-General Irina Bokova said this week . "I appeal to all parties to protect Palmyra and make every effort to prevent its destruction."