Hundreds of new refugees arrive in Herat daily
With winter cold now setting in and roads expected to be blocked by snow soon, tens of thousands of destitute people are trying to make their way westward to Herat, hoping to survive.
Mr Khan told the BBC that officials and Mujahideen commanders in the Ghor and Badghis provinces east and north of Herat had reported that an estimated 100,000 people were on the road trying desperately to get to Herat.
In Pakistan, meanwhile, aid and development agencies have started three days of talks on rebuilding Afghanistan, stressing the need to listen to the needs of the Afghans.
Seven million vulnerable
The conference, organised by the World Bank, the Asian Development Bank and the United Nations, hopes to find new ways to help Afghans reconstruct their country and economy, shattered after two decades of war.
Afghanistan has the largest refugee population in the world.
A UN official said there were up to seven million people in the country who were extremely vulnerable due to the continuing drought and fighting.
Mr Khan told the BBC that Herat and nearby refugee camps have already been swamped by hundreds of new arrivals every day. The camps are full and there are no facilities for the newcomers.
People dying
He said that if an immediate international relief operation was not forthcoming, a humanitarian disaster would be inevitable.
People are already dying, he said.
The borders with both Iran and Turkmenistan are now open and the roads to the stricken interior are secure. So there was no reason, he said, for an emergency relief operation not to be mounted.
There are already hundreds of thousands of refugees in the Herat area, with aid organisations struggling to meet their most basic survival needs.
Most of these refugees are not fleeing hostilities. They are the victims of the drought and famine that have resulted from three successive years with no rain.
Many of them had to sell their few remaining possessions to get money for their journey and they are left with absolutely nothing and no livelihood to go back to.
Processes interlinked
The BBC's Susannah Price in Islamabad says the aid and development agencies meeting there have called for Afghans to return from abroad to help the redevelopment process.
The conference coincides with the meeting of Afghan parties in Bonn to work towards a new government, and officials stressed that the two were interlinked.
One UN speaker pointed out that recovery and reconstruction would be essential to the political process just as the political process was essential for recovery and reconstruction.