The supreme leader of the Taliban warned Thursday against the danger of turncoats and infiltrators in the movement that has taken charge of Afghanistan.

Reflecting the seriousness of the threat, the reclusive Haibatullah Akhundzada issued a rare written public statement to urge Taliban commanders to purge their ranks.

In it he says "all those elders of their groups must look inside their ranks and see if there is any unknown entity working against the will of the government, which must be eradicated as soon as possible.

"Whatever wrong happens, the elder will be responsible for the consequences of the actions in this world and in the afterlife," he warned, in a statement tweeted out by multiple Taliban accounts.

The Islamist militant movement seized power in August after overrunning the capital and ousting the collapsing US-backed government, declaring a new Islamic Emirate of Afghanistan.

But after 20-years of guerrilla warfare, the Taliban has been forced to expand their ranks rapidly by recruiting former foes, allied Islamist militants and young madrassa students.

The Taliban's reclusive supreme leader Haibatullah Akhundzada rarely makes public statements, but made an exception to warn of extremist infiltrators
The Taliban's reclusive supreme leader Haibatullah Akhundzada rarely makes public statements, but made an exception to warn of extremist infiltrators Afghan Taliban / STR

Now that it is the government, the movement faces attacks in its turn from hardline factions like the Islamic State-Khorasan (IS-K).

The groups are now bitter rivals, but there has been movement between them over the years and they both employed tactics like suicide bombings and civilian massacres to destabilise the former regime.

On Tuesday, at least 19 people including a Taliban commander were killed in a gun and suicide bomb attack claimed by IS-K on a military hospital in the heart of Kabul.

Taliban commanders insist that they can re-establish stability and security, but there have also been killings blamed on Taliban elements or extremist infiltrators.

Last week, for example, gunmen who presented themselves as Taliban shot dead three wedding guests in a dispute about the playing of music, which the movement frowns upon.

Taliban spokesman insisted the killers were not acting under orders and promised they would be punished.

In his statement, Akhundzada said Taliban unit commanders must take the time to sit down with their recruits to "try to work on their manners and behaviour so that these mujahideen can work better for his leader."