Iraqi forces have recaptured the main government complex in Ramadi held by Islamic State since May, a day after the extremist group's leader said in a rare audio address that recent setbacks hadn't weakened the militants.

The reversal in Ramadi, located about 68 miles west of Baghdad, came after U.S. and coalition aircraft recently stepped up their bombing of Islamic State positions, including four airstrikes near the city Saturday targeting vehicles, weaponry, and tactical staging areas.

Islamic State fighters fled the Ramadi complex, which they had been using as a headquarters, with the arrival of Iraqi troops, CNN and Reuters reported, citing Iraqi government sources.

"The forces of the counterterrorism unit are now controlling the government compound," Sabah Noori, a spokesman for the Iraqi special forces, told the Washington Post. Pockets of Islamic State resistance are said to remain in the city.

There was a celebratory atmosphere in Baghdad, where state television showed images of people dancing and letting off fireworks as they waved the Iraqi flag in the streets, the Post reported.

A defeat in Ramadi would mark another step in attempts to reverse Islamic State's momentum in OPEC's second-largest producer, following the recapture of Tikrit this year. It would be a comeback of sorts for Iraq's troops, criticized by U.S. Defense Secretary Ash Carter as having had "no will to fight" when Islamic State overran the city in May.

Airstrikes by the U.S.-led coalition were intensified after the militant group claimed responsibility for the Paris terror attacks in November, which killed 130 people and injured hundreds more.

U.S. and coalition aircraft, including fighter jets and drones, conducted five strikes on Islamic State positions in Syria and 28 in Iraq on Saturday alone, the U.S. Department of Defense said. Initial reports showed that among the items destroyed were weapons, explosive caches, bridges, bunkers, and vehicles, the DOD said in a statement.

Saturday's audio message, which appeared on social media accounts and websites used by Islamic State, was the first to purportedly come from Islamic State's Abu Bakr al-Baghdadi since May. Baghdadi said his group had sustained setbacks before before in Iraq and Syria, only to return stronger.

He also addressed Israel, saying: "Palestine will only be your graveyard." That first explicit threat to Israel echoed a typical rallying cry used by Arab leaders for more than six decades.

Baghdadi's threat to Israel may reflect an attempt to garner support in the region by targeting a "common cause," according to Sultan Barakat, director of research at the Brookings Doha Center.