Fugitive Taliban leader tells insurgents they face sharia justice if found negligent in edict seen as attempt to win hearts and minds

Taliban foot soldiers will face sharia justice if they kill or injure innocent civilians without taking precautions, the fugitive leader of the Afghan insurgency has warned.

Mullah Omar, the Taliban's supreme cleric, released an 1,800-word statement that dwelled at length on the need to protect civilians in a sign of the insurgency's growing defensiveness on the issue.

Human rights workers described the statement, published in five languages on Friday to mark the Islamic festival of Eid, as extremely significant. They said it went into far more detail about the issue than any other previous pronouncement.

The mujahideen, as the rebels style themselves, are ordered to "take every step to protect the lives and wealth of ordinary people".

The decree said: "Scholars should be employed every now and then to preach protection of civilian life, wealth and honour to mujahideen and promote virtue … All civilian casualties which are caused or are believed to be caused by mujahideen should be reported to the superiors."

It also called for investigations by the movement's "legal offices" of cases where locals say civilians have been hurt by landmines, suicide bombings or other attacks. "If it is irrefutably proven that the blood of innocent Muslims is spilled by the negligence of mujahideen then a penalty should be implemented in accordance with sharia," the statement said. The family of the victims should also be compensated, it suggested.

Afghan civilians are also ordered to protect themselves by not "moving in close proximity to Americans who patrol in villages and countryside".

Kate Clark, a researcher at the Afghanistan Analysts Network, said even though the statement was in part propaganda it could also help civilians trapped in the middle of fighting between Nato and Taliban forces. "It is much, much more specific than ever before on the Taliban's system of internal discipline and command and control," she said. "And they admit that they themselves are causing civilian casualties, not just people doing it in their name."

That Omar's statement on the issue is an indication of how embarrassing the problem of civilian casualties has become for a movement that sees itself as the protector of the Afghan people against foreign military aggression.

According to the latest UN figures, the Taliban were responsible for 80% of the 1,462 civilian deaths caused by fighting between insurgents and pro-government forces in Afghanistan in the first six months of this year. Of those killed by insurgents, 38% of deaths were due to IEDs, or homemade roadside bombs.

Georgette Gagnon, the UN's director of human rights in Afghanistan, said it remained to be seen whether the insurgents would take any real steps to reduce casualties. "I would like them to say publicly that they will stop using indiscriminate, pressure plate IEDs," she said, saying that while in power the Taliban regime banned anti-personnel mines as un-Islamic.