WASHINGTON (Reuters) - The United States has carried out 70 to 80 air strikes against Islamic State in Afghanistan in the three months since U.S. forces were given broader authority to target the militants, a U.S. military spokesman said on Thursday.

Before January, the U.S. military could only strike Islamic State in Afghanistan under narrow circumstances, such as for protection of troops.

Military spokesman Brigadier General Charles Cleveland said the air strikes had decreased the capacity of the group in Afghanistan, where fighters loyal to Islamic State have emerged to challenge the larger Afghan Taliban in pockets of the country.

Cleveland said about 70 to 80 percent of the air strikes between January and the end of March were in the eastern Afghan province of Nangarhar.

“The capacity of Daesh, we believe has been lessened and their overall footprint in Nangarhar, we do believe, has been lessened as well,” Cleveland said. Daesh is an Arabic acronym for Islamic State.

The U.S. military has previously said there are between 1,000 and 3,000 Islamic State members in Afghanistan. Cleveland said that number was now probably closer to the lower estimate.

He said the group controlled about six to eight districts a few months ago, but that number was now closer to two to three districts.

“We do think that they still pose a potential real threat and again just based on their past performance, they have got the ability to catch fire very quickly,” Cleveland said.

He also said that the southern province of Helmand was not on the verge of falling into the hands of the Taliban, but it was a “difficult, contested area.” In February, Afghan forces pulled out of some parts of the province after months of heavy fighting with Taliban insurgents.

Helmand, a mainly desert region bordering Pakistan, is of strategic and symbolic importance as a heartland of the Taliban. The province sits along major smuggling routes for drugs and weapons. It accounts for the biggest share of opium cultivation, a principal source of revenue for the Taliban.

American troops have fought in Afghanistan since a U.S. invasion in 2001 that toppled the Taliban government that harbored the al Qaeda network responsible for the Sept. 11 attacks on the United States that killed about 3,000 people.

Cleveland added that there were still between 100 and 300 al Qaeda members in Afghanistan.

In October, the United States conducted more than 60 air strikes on an al Qaeda training camp and another site near Kandahar, the presence of which alarmed some analysts.