US forces attempted to rescue two American University of Afghanistan professors, who were kidnapped in Kabul in August, but failed as the hostages were not found at the raid location, according to a latest report. Afghanistan's Haqqani network was suspected of kidnapping the two professors, one of whom is an American and the other an Australian.

Seven militants were killed by American soldiers in a gun fight that erupted during the rescue operation launched in Jalalabad in eastern Afghanistan days after the two professors were taken hostage at gunpoint on 7 August, defence officials with the knowledge of the operation told Fox News. Officials added that none of the US soldiers were killed or wounded in the operation.

One of the officials reportedly said that it was not immediately clear if the hostages were ever inside the compound that was raided or if they were moved to some other location before the rescue attempt could take place.

This was the second rescue attempt made by US forces, after the first one was aborted due to absence of authorisation from the White House.

"It didn't go the way it was supposed to go," one official told the news network. "They turned back that first night because they didn't have authority. They could have gone without permission if they thought hostages' lives were in imminent danger," the official added.

Soon after the cancellation of the first mission, another request was sent to the White House that was immediately approved by President Barack Obama. One of the defence officials was quoted by the news network as saying that lack of consensus among the different government agencies led to the cancellation of the first mission.

US forces launched a rescue mission to free an American and an Australian professor abducted in Kabul, Afghanistan, but failed as the hostages were not found at the raid location - Representational image Wakil Kohsar/ AFP

"The president's swift approval provided the U.S. military the authorization to conduct the operation in Afghanistan," an official reportedly said.

"When the operation was launched, we believed the hostages were present at the location but unfortunately, they were not. The U.S. government's hostage recovery enterprise continues to work towards ensuring the hostages' safe recovery," the official added.

Meanwhile, Pentagon press secretary Peter Cook confirmed in a statement that Obama had approved the rescue mission at defence secretary Ash Carter's recommendation, but declined to divulge any other information. "We will not provide further information on this mission in order to protect the safety of hostages and operational security," Fox News quoted Cook as saying.