An Internet audiotape purported to be from an Al Qaeda commander who escaped from a U.S.-run prison in Afghanistan warns of increased attacks against international forces in the violence-plagued nation.

The message allegedly from Abu Yahia al-Libi, who escaped from Afghanistan's Bagram prison in 2005, appeared Friday. Its authenticity could not be verified, but it was posted on an Islamic militant Web site that carries militant statements.

Al-Libi said he also had a message to Al Qaeda leader Usama bin Laden. In the seven-minute recording, he assures bin Laden that insurgents ini Afghanistan have gotten stronger, calling them a "shining star in this dark age and a luminous moon in its dark sky."

The militants in Afghanistan "are going through continuous triumphs ... and are in a better shape compared with what they had been before," he said.

He said militants are "determined to turn the upcoming winter to hell for the infidels."

Afghan insurgents have been growing in strength, posing an increasing challenge to international forces trying to bolster the government. Militants killed more U.S. and NATO troops there in June than in Iraq for the second straight month.