KABUL, Afghanistan — Afghanistan said Saturday that recent U.S. airstrikes it assisted destroyed the top leadership of a fledgling Islamic State affiliate there, potentially striking a major blow to an insurgent group already targeted by local Taliban fighters.

While U.S. officials declined to confirm it, Afghan authorities said an American airstrike Friday killed Islamic State affiliate leader Hafeez Sayeed and more than 30 other militants. That comes after Afghan officials earlier said another U.S. airstrike killed the affiliate's second-highest official, Gul Zaman, and six others, including a former Pakistani Taliban spokesman named Shahidullah Shahid who earlier had joined the group.

"With the killings of Hafiz Sayeed, Gul Zaman and Shahidullah Shahid, who were the high-profile figures of Daesh inAfghanistan, we have destroyed the base of ISIS," said Abdul Hassib Sediqi, a spokesman for Afghanistan's National Directorate of Security, using two alternate names for the militant group.

Sediqi offered no photographs or other evidence to show the strikes killed the Islamic State affiliate's top leaders, though he said Afghan authorities verified a corpse from Friday's strike was Sayeed. Militants with the group have not discussed the strikes online.

NATO officials declined to immediately comment on the claim, saying they would issue a statement later Saturday. U.S. ArmyCol. Brian Tribus, a spokesman for U.S. Forces-Afghanistan, confirmed Americans carried out an airstrike Friday in Nangarhar'sAchin District, but declined to comment further.

NATO and U.S. officials have not commented on the strike that Afghan officials said killed Zaman and Shahid, which they said took place Monday in the same district as Friday's strike.

The Islamic State group, which holds a self-declared "caliphate" across roughly third of Syria and neighboring Iraq, has inspired militants across the greater Middle East and Africa to declare allegiance to its leader, Abu Bakr al-Baghdadi. The militants include those in Egypt who purportedly claimed a car bombing early Saturday at the Italian Consulate in Cairo that killed one person.

They also include militants in Pakistan and Afghanistan, the target of a U.S.-led invasion after the 2001 al-Qaida terror attacks on America.

Disenchanted extremists from the Taliban and other organizations, impressed by the Islamic State group's territorial gains and slick online propaganda, began raising its black flag in extremist-dominated areas of both countries in recent months.

Analysts and officials say the number of Islamic State supporters in the Afghan-Pakistan region remains small and that the group faces resistance from militants with strong tribal links. However, the rise of even a small Islamic State affiliate could further destabilize the region and complicate U.S. and NATO efforts to end the 13-year Afghan war.

In April, a motorcycle-riding suicide bomber attacked a line of people waiting outside a bank in eastern Afghanistan, killing at least 35 and wounding 125 in an assault the country's president blamed on the Islamic State group. Other violence has been blamed on the Islamic State affiliate, including gun battles between its followers and the Taliban, who warned the Islamic State group to stay out of the country. Afghan officials have suggested the Islamic State affiliate had a presence in three of its provinces, including Nangarhar, which borders Pakistan and frequently sees militants cross its borders.

Sediqi, the National Directorate of Security spokesman, said Afghan officials had created a special intelligence unit to target the Islamic State affiliate and its work directly aided the U.S. airstrikes.

"Daesh activities have been totally disturbed here and it is not easy for them to replace all these high-ranking figures any time soon," he said.

Meanwhile Saturday, the Britain-based Syrian Observatory for Human Rights said army airstrikes killed at least 28 people in the Islamic State-held town of al-Bab in northern Syria, including 19 civilians. The Local Coordination Committees group said the barrel bombings killed 29 people.

Al-Bab is a frequent target of Syrian army strikes that often kill civilians. On May 31, Syrian army airstrikes that hit a packed market in al-Bab killed around 70 people, most of them civilians.

Associated Press writers Eileen Sullivan in Washington, Zeina Karam in Beirut and Brian Rohan and Jon Gambrell in Cairocontributed to this report.