U.S. Defense Secretary Leon Panetta said on Friday militants who attacked the United States and its citizens will hunted down, in the first comments by a senior U.S. official on a hostage attack by Islamist militants in Algeria.

He said the U.S. government was working around the clock to ensure the safe return of its citizens caught up in the Algeria crisis.

A U.S. plane landed on Friday at an airport near a desert gas plant in Algeria where Islamist gunmen took hundreds of hostages to evacuate Americans caught up in the crisis, a local source said.