Nick Childs BBC foreign affairs correspondent

In the Afghan capital, Kabul, the UN's World Food Programme is beginning an emergency food distribution scheme for an estimated one million people.

A casual labourer here doesn't get enough money to provide for a family of six people, which is the average number of people in a family in Afghanistan

Khaled Mansoor UN spokesman

The WFP has employed more than 3,000 men and women in Kabul to carry out a survey and issue food tokens.

Hundreds of Afghan men and women are fanning out across the poorest parts of Kabul.

They will be surveying households over the next three days to decide how many people there are in each household and how urgent their need is.

Plummeting temperatures

They will also be distributing food coupons that will entitle a household to a 50-kilogram sack of wheat - enough, it is estimated, to last a month.

Purchasing power not supplies is the main problem

The UN spokesman, Khaled Mansoor, says food stocks themselves are not the issue.

"The problem that we have been facing for a long time is not really the availability of food but the purchasing power of the people, because a casual labourer here doesn't get enough money to provide for a family of six people, which is the average number of people in a family in Afghanistan."

Elsewhere in the country it is the descending temperatures which are concerning the aid agencies. Near Mazar-i-Sharif, in northern Afghanistan, some 150,000 people are living in flimsy tents as the freezing winter sets in.

"Obviously food is important but at the moment we are desperate to get quilts and warm clothing to these people," said Save the Children's Brendon Paddy.

"It's sub-zero temperatures in these camps. We've already had confirmed deaths of babies and infants."

Working women

The World Food Programme hopes to have its food distribution centres in Kabul ready by Sunday.

This is a one-off emergency effort and the WFP is employing large numbers of women, who were forbidden from working during Taleban rule.

It is both easier for them to gain access to households and a way of providing the women themselves with some income.

The survey team members are getting an average of $30 each.