"In every corner of the world, Muslims should be concerned about Afghan Muslims and help them," Mustafa Abu al-Yazid said on Wednesday in the audio message, according to SITE Intelligence Group, which monitors Islamist websites.

"Every Muslim who has the feeling of sacrifice in his heart should come forward and fight for the independence of Afghanistan," Yazid says in Arabic in the 28-minute audio, accompanied by a video showing him in a still image.

Yazid, in the speech titled "The Truth of Belief," also claims that insurgents are scoring victories in the battlefield despite the death of top Taliban military commander Mullah Dadullah in May.

Yazid calls on Muslims to support Dadullah's successor, Mullah Mansour.