The worst flooding in Pakistan's history has now affected¹ more than four million people and left at least 1,600 dead, says the UN.

联合国称，巴基斯坦历史上破坏性最大的洪水已使400多万人受灾、至少1600人死亡。

While floods in the north-west began to recede²（后退，减弱） , the vast body of water has been moving down the country into new parts of Punjab and menacing Sindh province.

All wells have been contaminated（污染） and water-borne diseases are spreading, officials say.

The region is midway through monsoon³（季风） season and more rain is forecast.

The number of affected districts in Punjab has reached seven, while 350,000 people have been moved from neighbouring Sindh province, most of which is on high alert, the United Nations said.

Manuel Bessler, who heads the UN Office for the Co-ordination of Humanitarian⁴ Affairs in Pakistan, told a news conference in Geneva: "What we are facing now is a major catastrophe⁵."

He added: "We are only in the middle of the monsoon season, there is more rain expected. We are afraid it will get worse."

With crops, homes, roads and bridges washed away, the human exodus⁶（大批的离去） continued on Thursday as yet more torrential rain fell.

Fleeing villagers have waded⁷ barefoot through water up to their necks and chests, carrying belongings⁸ on their heads.

Treetops visible

In Punjab, known as Pakistan's "breadbasket" for its rich agriculture, more than 1,300 villages have been affected and at least 25,000 homes destroyed, said disaster relief officials in the province.

In the worst-affected areas, small villages have been submerged（陷入水中） .

In large tracts⁹ of Kot Addu and nearby Layyah, water levels were so high only treetops were visible.

In Pakistani-controlled Kashmir, at least 20 people died when a bus plunged¹⁰ into a rain-swollen river.

At a refugee camp in Charsadda, Khyber Pakhtunkhwa (formerly North West Frontier) province, Tahir Shah, a doctor, said most patients coming to him were suffering from stomach problems, chest infections and skin problems, caused mainly by dirty flood water.

Meanwhile, forecasters warned of further downpours for the north-west; the region has not seen such flooding since 1929.

"The flood water is increasing at different points and we are expecting more rain in the next 24 hours," Hazrat Mir, chief meteorologist for Punjab, told news agency AFP.