US forces attempted hostage-rescue in Afghanistan: Pentagon

US forces in Afghanistan last month attempted to rescue two hostages, the Pentagon said Thursday, as US media reported the captives were two American University of Afghanistan professors.

"President Obama authorized US forces to conduct a mission in Afghanistan, aimed at recovering two civilian hostages," Pentagon press secretary Peter Cook said in a statement.

Nine killed as militants raid Kabul's American University

"Unfortunately, the hostages were not at the location we suspected. During the mission, US forces engaged and killed a number of hostile forces. No US personnel or civilians were harmed."

Two professors -- one American, the other Australian -- were seized from their vehicle August 7 in Kabul, as gunmen wearing police uniforms smashed the passenger window and hauled them away.

According to Fox News, which first reported the mission citing unnamed defense officials, the operation occurred a few days after the kidnapping.

The White House had scrapped a mission planned a day earlier because of differing assessments from intelligence agencies.

When the assault on a compound believed to house the hostages eventually occurred, they were not there, but seven enemy fighters were killed, Fox reported.

"Military hostage-rescue operations are inherently sensitive and dangerous and careful deliberation went into this mission," Cook said.

"The United States military remains fully prepared to take extraordinary steps to protect American citizens anywhere in the world."

Separately, American University was rocked by explosions and gunfire August 24 when militants stormed the facility in an incident that left 16 people dead.