The United States have more than doubled its airstrikes in Afghanistan to include positions of fighters who defected from Taliban to join Islamic State of Iraq and the Levant (ISIL), a US newspaper has reported.

The New York Times newspaper reported on Thursday citing US military statistics that the army intensified its air raids throughout June, raising the number of strikes to 106 compared to average 40 in previous months this year.

The publication said that according to Afghan officials the strikes against ISIL targets came partly at the request of the Afghan domestic intelligence service due to the risk of the group gaining a foothold in eastern Afghanistan.

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"We need to take action," the publication quoted one anonymous Afghan official as saying. "The willingness on the part on the part of the Americans to provide the air support is always there."

However, the American officials told the Times that the raids against ISIL were part of a defensive policy to protect the coalition forces from harm.

"The department anticipated a summer uptick in insurgent activity, and we were prepared to protect our forces," Henrietta Levin, a Pentagon spokeswoman, told the newspaper.

She also said the US was closely monitoring the growth of ISIL in Afghanistan to see if it has a "meaningful impact".