US air strikes kill dozens of Yemen's al-Qaeda militants
At least 28 al-Qaeda militants have been killed by US airstrikes in Yemen since September, Washington confirmed this week.
The terror network lost dozens of its fighters in the past three months, a statement released on Thursday suggested.
Army Maj. Josh T. Jacques, a spokesman, said the strikes "pressure the terrorist network and hinder their ability to attack the US and our allies".
Yemeni authorities have for months pressed a campaign against militants who remain active in the south and east of the impoverished Arabian peninsula country.
IS and its militant rival al-Qaeda have taken advantage of a conflict between the government and Yemen's Houthi rebels - who control the capital Sanaa - to bolster their presence across much of the south.
The two armed militant groups have carried out a spate of attacks in Aden, Yemen's second city and headquarters of the internationally-recognised government whose forces retook the port city from the Houthis last year.
Al-Qaeda has long been the dominant militant force in Yemen, located next to oil-flush Saudi Arabia and key shipping lanes, but experts say IS is seeking to supplant its extremist rival.
Washington regards al-Qaeda's Yemen-based branch as its most dangerous and has kept up a long-running drone war against its commanders.
In August, an IS militant rammed his explosives-laden car into an army recruiting centre in Aden, killing 71 people in the deadliest attack on the city in over a year.
A Saudi-led coalition has since March 2015 supported loyalist forces fighting the Houthis.
The Arab coalition intervened after Houthi rebels allied with troops loyal to Yemen's former President Ali Abdullah Saleh seized the capital Sanaa and overran other parts of the country.
[Agencies contributed to this story]