KABUL -  An American and an Australian have appeared in a Taliban hostage video, five months after they were kidnapped from Kabul.

Gunmen wearing police uniforms abducted American Kevin King and Australian Timothy Weekes, both professors at the American University of Afghanistan, on August 7, seizing them from their vehicle after smashing the passenger window.

The 13-minute, 35-second video circulated by Taliban spokesman Zabihullah Mujahid on Wednesday offers the first apparent proof that they were still alive.

Australia said Thursday it "has been working closely with other governments to secure the release" of the hostage, but would not elaborate citing his family's wishes and safety concerns.

The video comes after US Special Operations forces conducted a failed secret raid in August to rescue them.

President Barack Obama authorised the raid in an unspecified area of Afghanistan but the hostages were not there, the Pentagon said in September.

The elite American University of Afghanistan, which opened in 2006 and has attracted a number of faculty members from Western countries, called on the Taliban to release them immediately.

"Kevin and Tim came to Afghanistan as teachers, to help Afghanistan," the university said in a statement. "These innocent people have done nothing to harm anyone."

The abductions highlighted the growing dangers faced by foreigners in Afghanistan.

The Afghan capital is infested with organised criminal gangs who stage kidnappings for ransom, often targeting foreigners and wealthy Afghans, sometimes handing them over to insurgent groups.