US: Death of thousands of ISIS militants in three months has weakened the group

The United States-led coalition has killed over 6,400 members of the Islamic State (ISIS) terrorist group according to its own statistics.

The intensified air strikes coupled with ground offensives against ISIS by other rebel groups have lead US commanders to argue that the group is gradually being weakened decisively.

"We are noticing that they are not quite the same skill level that they once were," a top coalition commander, Lt. Gen. Sean MacFarland, told USA Today. "Maybe they're having trouble replacing quality with quality."

Lt. Gen. Sean MacFarland explained that more ISIS members are defecting and the group has failed to mount any offensives to make-up for its recent losses on the battlefield. "We take that as a positive indicator that we're starting to hit them where it hurts," he remarked.

Coalition statistics indicate that on average 500 ISIS members have been killed a week over the course of the last three months. Since the campaign started a year-and-a-half ago about 25,000 members of ISIS are believed to have been killed by coalition air strikes.