WASHINGTON (AP) — The State Department said it is evaluating a video released by the Afghan Taliban showing a Canadian man and his American wife warning that their Afghan captors will kill them unless the Kabul government ends its executions of Taliban prisoners.

State Department spokesman John Kirby said at his daily briefing Tuesday that the video purportedly showing Canadian Joshua Boyle and American Caitlan Coleman is "being examined for its validity."

Kirby says the U.S. government is concerned about the couple's welfare and urged "their immediate release on humanitarian grounds."

In the video, Boyle and Coleman call on Canada and the United States to pressure the Afghan government into changing its policy on executing captured prisoners.

Boyle and Coleman were seized in 2012 while traveling in a mountainous region near the Afghan capital, Kabul.