KABUL (AFP) - The family of deceased Taleban leader Mullah Omar has refused to pledge allegiance to his successor, calling on religious scholars to settle a growing rift within insurgent ranks over the power transition.

Mullah Akhtar Mansour was announced as the new Taleban chief on Friday after the insurgents confirmed the death of Mullah Omar, who led the militant movement for some 20 years.

But splits immediately emerged between Mansour and those who challenged his appointment, including the late leader's son Yakoub and his brother, Mullah Abdul Manan.

"Our family... has not declared allegiance to anyone amid these differences," Manan said in an audio message released Sunday, without naming Mansour.

"We want the ulema (religious scholars) to resolve the differences rather than declaring allegiance to any side," said the audio message, which Taleban sources confirmed was from Manan.

"Our family will serve the new leader... if he is elected with consensus."

Mansour on Saturday called for unity in the Taleban in his first audio message since becoming head of the group as it faces its biggest leadership crisis in recent years.

His comments were apparently aimed at averting a factional split at a time of growing discord over the direction of peace talks with the Afghan government.

- 'Did they deceive us?' -

Yakoub and several other members of the Taleban's ruling council walked out of the meeting at which Mansour was declared leader, refusing to pledge allegiance to him, a Taleban source told AFP.

"Part of the insurgency is troubled and needs answers from Mansour and his allies: why did they hide Mullah Omar's death all these years? Did they deceive us by putting out fake statements in his name just to serve their own interests?" he said.

The Taleban have not revealed when Omar died but the Afghan government said he passed away in Karachi in April 2013.

But official Taleban statements in the name of Omar, who had not been seen in public since the Taleban were toppled from power in 2001, were released as recently as last month.

Another commander linked to the Quetta Shura, the Taleban's ruling council based in the southwestern Pakistani city of Quetta, criticised Mansour's selection process.

He told AFP only a handful of the 20-member shura backed Mansour.

Many militants also oppose what they see as Pakistan's attempt to force the Taleban into direct peace talks with the Afghan government.

Mansour and his two newly named deputies - influential religious leader Haibatullah Akhundzada and Sirajuddin Haqqani - are all seen as close to the Pakistani military establishment, which has historically nurtured and supported the Taleban.

But despite the open rifts the Taleban have sought to present a unified front, posting video and audio messages on their official website of fighters pledging loyalty to Mansour.

A senior member of the Haqqani network, the feared Taleban group led by Sirajuddin Haqqani, urged fighters to unite behind Mansour.

He told AFP the present discord "undermines the movement and will benefit the foreign forces".

Mansour is seen as a pragmatist and a proponent of peace talks, raising hopes that the power transition could pave the way for an end to Afghanistan's long and bloody war.

The announcement of Omar's death, however, cast doubt over the fragile peace process, forcing the postponement of a second round of talks that had been expected in Pakistan last Friday.