(Credit: Courtesy of U.S. Army, Tech. Sgt. Andy Dunaway/Wikimedia Commons)

WASHINGTON - The U.S. has begun using Apache AH-64 attack helicopters to strike at ISIS targets inside Iraq, the first time the aircraft have been used for offensive strikes since arriving in Baghdad in early July.

Their use opens up a new capability in the airstrike campaign against ISIS in Iraq, but one that also comes with risks, as they could be vulnerable to ground fire.

A defense official confirms that Apache helicopters were used this weekend as part of four airstrikes on a large ISIS force northeast of Fallujah. The attack was conducted in coordination with Air Force fighter aircraft that supported the operation.

A press release by U.S. Central Command said the air strikes near Fallujah "struck two mortar teams, a large ISIL [ISIS] unit and two small ISIL units."

The official confirmed that the strikes were the first use of the Apache helicopters that were deployed to Iraq in early July.

Several Apache helicopters were included in an additional deployment of several hundred U.S. military personnel sent to Baghdad o reinforce security at U.S. embassy facilities and access to the Baghdad Airport.

The deployment of the attack helicopters was intended to be defensive nature, but their offensive capabilities are now being used against ISIS. Any restrictions on their use for offensive purposes were presumably lifted in early September when President Obama announced that offensive air strikes could be used against ISIS targets.

Apache helicopters can be used to provide close air support for ground troops, but can also fire Hellfire missiles at enemy targets from several miles away. The use of long-distance sensors and missiles lessens the potential exposure to small arms fire the helicopters could face in a ground combat situation. The aircraft are still vulnerable to small arms and missile fire, however, and during the war in Iraq several were shot down by enemy fire.

The defense official said the strikes northeast of Fallujah were coordinated with Iraqi security forces to support their operations.

"It's a capability we have, that they asked for, and that could contribute to their operations" the official said.

In recent weeks Iraqi security forces have struggled against ISIS forces that have attacked several cities in Anbar Province west of Baghdad. ISIS victories there could pose an even greater security threat to Iraq's capital.

As of Friday the Pentagon said it had conducted 334 airstrikes against ISIS - 248 in Iraq and 86 airstrikes in Syria.

Iraq has used a limited number of Russian-made attack helicopters against ISIS and has long sought to acquire Apache helicopters. In January the Pentagon announced the potential sale to Iraq of 24 of the aircraft for $4.8 billion, but so far Iraq has not indicated it will purchase the aircraft.