U.S. Strikes Have Killed 1,100 ISIS Fighters And Cost $1 Billion

U.S.-led coalition airstrikes on Syria have killed more than 1,100 Islamic State fighters since the bombings began in September, according to a British-based monitoring group.

The Syrian Observatory for Human Rights said on its website Tuesday that it documented the deaths of 1,171 people, with at least 800 others wounded. Most of those killed by the international airstrikes that began Sept. 23 were members of ISIS, the website noted. The number of dead included 52 civilians.

The monitoring group, which relies on a network of activists and hospitals in the region, added:

"We, in SOHR, believed that the real number of casualties in ISIS is more than our number, because there is absolute secrecy on casualties and due to the difficulty of access to many areas and villages that have witnessed violent clashes and bombardment."

Casualty figures are impossible to verify. But the Syrian Observatory for Human Rights is considered the most reliable resource in a sea of misinformation. The U.N., media organizations and military analysts regularly cite numbers put out by the group run by a Syrian who now lives in England.

In related news, on Monday the Pentagon announced it had spent more than $1 billion fighting ISIS since the airstrikes began.

"As of Dec. 11, 2014, the total cost of operations related to [ISIS] since kinetic operations started on Aug. 8, 2014, is $1.02 billion and the average daily cost is $8.1 million," Pentagon spokesman Bill Urban said.

The Pentagon had previously stated the average daily cost to be more than $7 million a day. That number rose because of the number of airstrikes and related costs, a defense official told Agence France-Presse.

In total, the United States carried out 488 airstrikes in Syria through Dec. 15, according to U.S. military data published by Reuters.

The Hill newspaper reported that the military's ISIS campaign will get its own inspector general to oversee government spending. Jon T. Rymer, the current Pentagon inspector general, will lead oversight efforts into Operation Inherent Resolve.