The Afghan President, Hamid Karzai, has banned political leaders from taking part in military activity.

The move is being seen as Mr Karzai's first major attempt to rein in the country's powerful warlords.

Karzai is struggling to enforce peace beyond Kabul

The decree, which comes into immediate effect, was released as the president arrived in Oslo ahead of a conference on Afghan reconstruction.

It says that in order to ensure affairs are better run, no civilian or military official is allowed to work in both political and military spheres.

Observers say dominant regional chiefs represent the biggest challenges to Mr Karzai's rule.

Since the collapse of the Taleban last year, regional warlords have continued to use violence to resolve ethnic and territorial disputes.

Calling the shots

The warlords include Ismail Khan in the west, Abdul Rashid Dostum in the north and Gul Agha in the south.

So far Mr Karzai has been powerless to impose his authority across the country.

Ismail Khan has been battling rivals in the west

Mr Khan, an ethnic Tajik who controls Herat province, has allowed his forces to engage in frequent clashes with rival ethnic groups in his area of control, despite government attempts to mediate peace.

In the latest outbreak earlier this month, fighting between supporters of Mr Khan and those of Pashtun commander Amanullah Khan left at least 11 people dead.

During the clashes a US B-52 plane dropped bombs in the area - the first time such raid in the country in five months.

However, the Americans say they are staying out of factional conflict, and the air assistance was called in by US special forces after they came under fire on the ground.

Under reconstruction

Correspondents say the decree also represents a direct challenge to General Dostum, an Uzbek leader who controls large tracts of Afghanistan's strategic north.

A former communist general, he is the head of the military-backed Junbish political party.

After signing the decree President Karzai went to Norway, where an international donors' conference is to be held on Tuesday and Wednesday.

On Monday Mr Karzai is due to have meetings with the Norwegian ministers for foreign affairs, defence and aid.

Afghan officials say the conference in Oslo will look at ways of redefining Afghanistan's needs as humanitarian relief gives way to longer term plans for the reconstruction of the country.