The militant leader, Abdul Hasib, had overseen a number of bloody attacks that directly challenged the authority of President Ashraf Ghani, including a massacre at the main Afghan Army hospital in Kabul that killed at least 50 people.

Mr. Hasib was killed in an operation on April 27 in eastern Nangarhar Province, along the border with Pakistan, according to the statement by Mr. Ghani’s office. The statement said the government had waited for verification that Mr. Hasib had been killed in the raid before announcing his death. It did not say how his death had been confirmed.

The United States military command in Afghanistan said in a statement on Sunday that American forces had participated in the raid that killed Mr. Hasib and up to 35 other militants.

It was the second time in nine months that the leader of the ISIS in the Khorasan, as the Afghanistan affiliate is known, was killed, Gen. John W. Nicholson, the commander of American forces in the country, said in the statement. Mr. Hasib’s predecessor, Hafiz Saeed Khan, was killed in July in a United States airstrike; he had been reported dead a few times before the American military confirmed it in August.

The United States military command in Afghanistan had said that an operation on April 27 targeted Mr. Hasib. Two American Army Rangers, Sgt. Joshua Rodgers and Sgt. Cameron Thomas, were killed in the operation, perhaps by so-called friendly fire, the Pentagon has said.

Afghan and American forces often go on joint missions. The one that killed Mr. Hasib included about 50 United States Army Rangers and a similar number of Afghan special security forces, the Pentagon has said. A firefight broke out during the raid, which lasted over three hours, and American F-16 fighter jets and Apache attack helicopters carried out airstrikes to protect the troops.