By Catherine Davis BBC correspondent in Kabul

A new national army is emerging in Afghanistan

At an official ceremony just outside Kabul, the Afghan leader, Hamid Karzai, urged the soldiers to make their contribution to the country's reconstruction.

Plans for a 70,000-strong national army were unveiled by the president late last year.

The challenge is how to create a nationally recognised force in a country long used to private militias and where security remains a daily concern.

The two brigades marched proudly past President Karzai and senior military officials, before standing to attention on a muddy plain flanked by snow-capped mountains.

Symbolic significance

President Karzai paid tribute to those who had already given their lives for Afghanistan, and he thanked the United States and others for helping train and equip the new army.

In his address, the commander of the international forces here said the brigades represented a modern Afghan army, an army standing for all the people of Afghanistan.

The so-called activation of these two brigades has symbolic significance - one observer said it showed the national army was an established organisation within the government and that it had an authoritative presence in the country.

But there is still a long way to go.

Around 2,000 soldiers are said to have been trained so far, while thousands of other Afghans carry arms, and local warlords remain powerful figures.