The United Nations expressed fears Thursday that flood-affected people in Pakistan's southwestern province of Baluchistan could move toward Iran, sparking illegal cross-border movements.

Baluchistan, which July 22 became the first of Pakistan's provinces hit by flash floods that have since submerged one-fifth of the country, borders Iran's restive Baluchistan-Sistan province, where the anti-Iran Jundollah militant organisation has been active.

More than 2 million people have been affected in the impoverished province, and at least 1 million are living in relief camps, where the Office of the UN High Commissioner for Refugees described their situation as 'disgusting'.

'Our concern is that if the needs of these people are not fulfilled, they might start moving toward the Iranian border,' said office representative Mengesha Kebede, who just returned from a mission to Baluchistan.

Iran, wary of any mass movement toward its sensitive border, has already asked the UN to keep it updated about such movements.

Baluchistan has largely been neglected by aid organisations and private charities, leaving the Pakistan Army to carry out the bulk of flood relief there. The army, however, is not popular in the province, where nationalists have been fighting a low-intensity separatist war.

Pakistan is seeing the worst flooding in its history, which has displaced more than 18 million people and swamped agricultural land.

Prime Minister Yousuf Raza Gilani said Wednesday that the net economic losses inflicted by the floods and rains might rise to $43 billion.

The floodwaters have begun to fall, but it would take weeks before displaced people are able to move from their temporary shelters, where aid workers are struggling to provide emergency relief and prevent waterborne diseases.

The UN appealed for $460 million to meet the emergency needs of the flood victims, and so far, it has received $325 million in aid. The international community has also directly provided funds to Pakistan, taking the total amount to $1 billion.