Catholic Relief Services (CRS) on Thursday said a team of six doctors which had surveyed villages along a 60km stretch of highway in the province of Ghor were told of 140-150 child deaths.
Most of the deaths appeared to have been caused by pneumonia and most were of children under the age of five, Paul Hicks, director of CRS for western Afghanistan said.
"These are still unconfirmed numbers, based on reports the teams are getting from talking to families and community leaders," he said.
Hicks said the doctors reported 100% rates of anaemia - where there are not enough red blood cells in the blood - and high rates of severe malnutrition among children, with the rate for under fives ranging from 10% to 20%.
More feared dead
Hicks said aid workers feared the toll in remote regions of the province, which relief workers had been unable to reach because of heavy snow, could be higher.
"Several hundred children may have died," he said.
He expressed frustration that aid teams had been unable to reach remote parts because of a lack of helicopters from the US military or the United Nations.
Doctors reported 100% rates of
anaemia among children
"We have not been able to get air support, and for the past three weeks we have not been able to get people into these areas," he said.
"It is a matter of resources and priorities. The US military has not been able to provide resources and the UN has only one helicopter available, which cannot possibly meet the needs."
The US military said it plans to fly a C-130 transport plane mission over Ghor on Friday to drop 16 pallets of food supplied by the UN World Food Programme.
But Hicks said there was a need to get survey teams on the ground to assess what emergency supplies, such as food, fuel and medicines were needed throughout the province.
"There is a special need for fuel," he said. "There has been especially high snowfall and there are a lot of families who didn't prepare enough fuel stocks to get them through the winter.
"According to some reports we are hearing, some families are having to pull wood from the roofs of the houses to burn"
Paul Hicks, CRS director for western Afghanistan
"According to some reports we are hearing, some families are having to pull wood from the roofs of the houses to burn."
The Ghor provincial government said last week it had confirmed 136 deaths, mostly of children, in four districts but the real toll may be more than 300.
The Ministry of Heath has dismissed concerns expressed by CRS last week that more than 1000 children may have died in Ghor in what has been one of its worst winters for years.
Health Minister Sayyid Muhammad Amin Fatemi has played down the figures, saying on Wednesday that the number of confirmed child deaths caused by cold weather throughout the country in the past six weeks was 211.
Hicks said ministry statistics came only from areas that had health clinics. Since few villagers could access these, most deaths went unrecorded.