Eight Americans were killed in an explosion at a U.S. compound in Afghanistan Wednesday, officials said.

Afghan officials said a suicide bomber had entered a U.S. facility.

A U.S. official in Afghanistan would not confirm the report of a suicide bombing, saying an investigation is under way. The official said the attack occurred at a U.S. military base in southeastern Afghanistan’s Khost province and that all of those killed were Americans.

A spokesman for the U.S. military in Afghanistan said none of the dead were soldiers and that the attack was not on a U.S. military base, but at a facility associated with the U.S. Embassy.

The U.S. Embassy declined to comment ahead of an announcement scheduled for Thursday morning, Afghanistan time, by U.S. Ambassador to Afghanistan Karl Eikenberry.

Iran’s state-owned Press TV had reported five U.S. troops and four Afghan soldiers were killed in the blast and that the Taliban had claimed responsibility for it.

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