KABUL (REUTERS) - The Taleban condemned a video released this week showing what appeared to be a group of fighters belonging to the radical Islamic State in Iraq and Syria (ISIS) movement killing a group of Afghan prisoners by blowing them up with explosives.

The video, apparently shot in the eastern Afghan province of Nangarhar in June, gave a glimpse into the struggle the Taleban is waging against Islamic State - both considered ultra-hardline groups - for supremacy of the Islamist insurgency in Afghanistan.

"A horrific video was released yesterday showing kidnappers who associate themselves with Daesh (Islamic State) brutally martyring several white-bearded tribal elders and villagers with explosives," said a statement posted on the Taleban's website.

The Taleban, which itself if frequently accused of brutality against Afghan government soldiers that it captures, said prisoners should never be treated in such a manner.

"This offence and other such brutal actions by a few irresponsible ignorant individuals under the guise of Islam and Muslims are intolerable," it said.

Groups associated with ISIS have made growing inroads in Afghanistan in recent years, attracting fighters and support away from the Taleban by preaching a more extreme form of Islamist militancy.

The video contained a message in Arabic and a Pashto language commentary which said that a group of what it called "apostates" had been captured following a battle between ISIS fighters, Taleban and Afghan government forces.

The bound captives appear to have been local men who had fought with or helped the Taleban.

After showing the explosion which killed the men, the video ends with a message in Arabic urging local people to heed the lesson.

"Do you have a taste for digging your own graves? Do you want to be beheaded?" a man's voice asks.